modern approach to hvac design and its future trend

MODERN APPROACH TO HVAC DESIGN AND

ITS FUTURE TREND

A dissertation submitted to the Department of Pharmacy,

The University of Asia Pacific in the partial fulfillment of the

requirements for the degree of Master of Pharmacy in

Pharmaceutical Technology

SUBMITTED BY

Md. Hasif Sinha

Registration No: 09207021

Roll No: 21

DEPARTMENT OF PHARMACY

The University of Asia Pacific

Date of Submission: October 18, 2010

Table of Contents

i

Table of Contents

Purpose of the Study _________________________________________ vi

Abstract ___________________________________________________ vii

List of Chapters

Chapter

No.

Chapter

Name

Page

No.

1 Introduction to HVAC 1

1.1

1.2

1.3

1.4

1.4.1

1.4.2

1.4.3

1.4.4

1.4.5

Introduction

Objective of HVAC System

Scope of Modern HVAC

HVAC System

Types of HVAC Systems

Heating

Ventilating

Air-Conditioning System

Efficiency

1

1

1

2

2

3

3

3

4

2 HVAC System Choosing and Designing 5

2.1

2.1.1

2.2

2.2.1

2.2.2

2.2.3

2.2.4

2.2.5

2.2.6

2.3

2.3.1

2.4

2.4.1

2.4.1.1

2.4.1.2

2.4.1.3

2.4.1.4

2.4.1.4.1

2.4.1.4.2

2.4.1.4.3

Choosing an HVAC System

HVAC System Selection Guidelines

Choosing an Air-Conditioning System

Building Design

Location Issues

Utilities: Availability and Cost

Indoor Requirements and Loads

Client Issues

System Choice

Unitary System Selection Guidelines

Factors to Consider When Selecting Unitary Systems

HVAC Design

Design of an Air Handling Unit

Sub-Systems of AHU

Air Flow Patterns

Filters Positions

Air Circulation System

Air Re-Circulation

Ventilation with 100% fresh air (no air re-circulation)

Ventilation with re-circulated air with make-up air

5

5

6

6

6

7

7

7

7

8

8

8

8

8

9

11

12

12

13

13

Table of Contents

ii

3 Zoning Design, Central Plants and Hydronic Systems 14

3.1

3.1.1

3.1.2

3.2

3.2.1

3.2.2

3.2.2.1

3.2.2.2

3.2.2.3

3.2.2.4

3.3

3.3.1

3.3.2

3.3.3

3.3.4

3.3.5

3.3.6

3.3.7

3.4

3.4.1

3.4.1.1

3.4.2

3.4.3

3.4.3.1

3.4.4

3.5

3.5.1

3.5.2

3.5.3

3.5.4

3.5.5

3.5.6

3.6

3.6.1

3.6.2

3.6.3

3.6.4

3.6.5

Zone

Zoning Design

Controlling the Zone

Single Zone Air Handlers

Examples of Buildings with Single-zone Package Air-

Conditioning Units

Air-Handling Unit Components

Refrigeration Equipment

System Performance Requirements

Rooftop Units

Split Systems

Multiple Zone Air Systems

Three Deck, Multizone System

Dual Path, Outside Air System

Single-Duct, Zoned Reheat, Constant Volume Systems

Single-Duct, Variable Air Volume Systems

Dual-Duct, Variable Air Volume System

By Pass Box Systems

Constant Volume Dual-Duct, All-Air Systems

Central Plants

Boilers

Boiler Components

Water Chillers

Centrifugal Water Chillers

Central Plant Water Chiller Optimization

Cooling Towers

Hydronic Systems

Natural Convection and Low Temperature Radiation

Heating Systems

Panel Heating and Cooling

Fan Coils

Fan Curves

Two Pipe Induction Systems

Water Source Heat Pumps

Hydronic System Architecture

Steam Systems

Water Systems

Hot Water Systems

Chilled Water Systems

Condenser Water System

14

14

15

15

15

16

17

17

17

18

18

19

19

19

20

20

20

21

21

22

22

23

24

24

25

25

26

27

27

28

28

29

29

29

29

30

30

30

Table of Contents

iii

4 Control Systems and Thermal Comfort 31

4.1

4.2

4.3

4.4

4.4.1

4.4.2

4.4.3

4.4.4

4.4.5

4.4.5.1

4.5

4.5.1

4.5.1.1

4.5.1.2

4.5.1.3

4.5.1.4

4.5.1.5

4.5.1.6

4.6

4.7

4.7.1

4.7.2

4.7.3

4.8

4.8.1

4.8.1.1

4.8.1.2

4.8.1.3

4.8.1.4

4.8.1.5

4.8.1.6

4.8.1.7

4.9

4.9.1

4.9.1.1

4.9.1.2

4.9.1.2.1

4.9.1.2.2

4.9.1.2.3

4.9.1.3

4.9.2

4.9.2.1

4.9.2.1.1

4.9.2.1.2

4.9.2.1.3

HVAC Control Systems

Control Loops

Control Modes

Control Types

Self-powered Controls

Electric Controls

Pneumatic Controls

Electronic Controls

Direct Digital Controls, DDC

Benefits of DDC

Control System Components

Controllers

Single Pressure Thermostat

Dead Band Thermostat

Dual Pressure Thermostat

Humidistat

Master/Submaster Controller

Receiver-controller and Transmitter

Energy Conservation

Parameters to Control

Importance of Humidity Control

Importance of Temperature Control

Importance of Dust Particle Control

Thermal Comfort

Factors Influencing Thermal Comfort

Activity Level

Clothing

Occupants Expectations

Air Temperature

Radiant Temperature

Humidity

Air Speed

Heat Flow and Heat Recovery

Heat Flow

Heat Transfer

Types of Heat Transfer

Conduction

Convection

Radiation

Heat Transfer Equations

Heat Recovery

Heat Recovery Systems

Comfort- to-Comfort Heat Recovery Systems

Process-to-Comfort Heat Recovery Systems

Process-to-Process Heat Recovery Systems

31

31

32

32

32

32

32

32

32

33

33

33

33

33

34

34

34

34

34

35

35

36

36

36

36

37

37

37

37

38

38

38

38

38

38

38

39

39

39

39

39

39

40

40

40

Table of Contents

iv

5 Future Trend to HVAC 47

5.1

5.2

5.3

5.4

5.5

5.6

5.7

Future Trend to HVAC

Future Revolution in HVAC Design

Logic of the HVAC Revolution

Optimized Function HVAC Design

Central Plant Equipment in Optimized Systems

Economics of Optimized-Function HVAC

Onward to the Future

41

41

41

42

42

42

43

6 Conclusion 44

6.1 Conclusion 44

List of Figures

Figure

No.

Figure

Headline

Page

No.

1.1 Air-Conditioning Plant 4

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

Sub-systems of AHU

(a) Turbulent Air Flow, (b)Uni-directional or Laminar Air Flow

Room 1, 2 & 3 with different air flow patterns and exhaust systems

AHU mounted final filter

Filter in terminal position

HVAC installation feeding 3 rooms

HVAC installation feeding 2 rooms

Ventilation with 100% fresh air (no air re-circulation)

Ventilation with re-circulated air with make-up air

9

10

10

11

11

12

12

13

13

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

3.10

3.11

3.12

3.13

3.14

3.15

3.16

3.17

3.18

3.19

3.20

Building Plan

Single Zone Rooftop Air-Conditioning Unit, Energy Supplies

Air-Conditioning System: Single-Zone Air Handler

Basic Vapor Compression Refrigeration Cycle

Rooftop Unit

Split System

Mixing at the Air Conditioning Unit in a Multizone System

Reheat System

Variable Air Volume System

By-Pass Boxes on Each Zone

Dual-Duct System, Double Line Diagram

Hot Water Heating System with Two Boilers

Water Chiller with Water Cooled Condenser

Two Chiller Piping with Constant Chiller Flow

Centrifugal Mechanical Chiller

Typical Natural-Draft Open Cooling Tower

Induced Draft, Closed Circuit Cooling Tower

Wall-Mounted Single and Double Panel Radiators

Concrete Radiant Floor

Typical Fan-Coil Unit

14

16

16

17

18

18

19

20

20

21

21

22

23

24

24

25

25

27

27

28

Table of Contents

v

3.21

3.22

3.23

3.24

Induction Unit

Steam System

Chiller System with Decoupled Flows

Evaporative Cooling Tower

28

29

30

30

4.1

4.2

Diagram of Control Loop

DDC Control Schematic

31

33

References

Purpose of the study

vi

Purpose of the Study

The purpose of the study on the topic Modern Approach HVAC Design and its

Future Trend is enormous. The main focus is on the proper choosing and designing

of HVAC systems in order to achieve more reliable, dynamic and successful future in

the pharmaceutical industries HVAC systems. To maintaining the air cleanliness we

need to prepare perfect HVAC design and control systems. The air pressure, air flow

velocity, direction of air flow, make-up and fresh air flow system, air filtration and

other environmental factors such as temperature and humidity should be controlled

properly. The HVAC systems are divided into components and controls for air, water,

heating, ventilating and air conditioning to clearly illustrate the way in which each

system, subsystem, control or component contributes to providing the desired indoor

environment. There are several zone air systems in the pharmaceutical industry like

single zone air system and multiple zone air systems. The building, zoning areas,

machineries, and equipments should be design perfectly to control the air cleanliness,

particle contaminations, and cGMP regulations. We also need to focus on cost

effectiveness of the HVAC system. Some of the many cost concerns include initial or

installation cost, operating and maintenance cost, and equipment replacement costs.

Another cost concern that may be overlooked by the designer is the cost associated

with equipment failure. The best situation is when designer and owner are both

involved in the HVAC selection process. So the proper designing of an HVAC system

is not an easy process. The core purpose of an HVAC system is to provide and

maintain environmental conditions within an area. The type of system selected is

determined by the mechanical designers knowledge of systems and the building

owners financial and functional goals.

Abstract

vii

Abstract

HVAC is particularly important in the design of medium to large industrial and office

buildings where safe and healthy building conditions are regulated with temperature

and humidity, as well as "fresh air" from outdoors. Depending on the complexity of

the requirements, the HVAC designer must consider many more issues than simply

keeping temperatures comfortable. The proper design of HVAC system is one of the

most fundamental factors for the pharmaceutical industries. The engineers are trying

to modernization the HVAC design on the focusing of various important factors such

as zoning design, central plants, hydronic systems, thermal comfort, and control

systems. Systems have been designed for greatest assurance of consistent

environmental conditions, with constant volume or reheat and high air change rates

the order of the day. Steps to prevent cross-contamination in multi-product plants

have been draconian, ranging from 100% fresh air or exhaust to multiple series HEPA

filters in supply and exhaust. Developments in processing equipment, isolation

technology and a risk or science-based approach to ensuring parameters of "strength,

identity, safety, purity, and quality," open a new world of possibilities for HVAC in

pharmaceutical facilities.

CHAPTER ONE

Introduction to HVAC

Chapter - 1 Introduction to HVAC

Modern Approach to HVAC Design and its Future Trend 1

1.1 Introduction

HVAC an initialism that stands for the closely related functions of "Heating,

Ventilating, and Air Conditioning" the technology of indoor or automotive

environmental comfort. HVAC system design is a major sub-discipline of mechanical

engineering, based on the principles of thermodynamics, fluid mechanics, and heat

transfer. Refrigeration is sometimes added to the field's abbreviation as HVAC&R or

HVACR, or ventilating is dropped as in HACR.

HVAC is particularly important in the design of medium to large industrial and

office buildings where safe and healthy building conditions are regulated with

temperature and humidity, as well as "fresh air" from outdoors.

Depending on the complexity of the requirements, the HVAC designer must

consider many more issues than simply keeping temperatures comfortable. We need

to discuss about the fundamental concepts that are used by designers to make

decisions about system design, operation, and maintenance.

1.2 Objective of HVAC System

The goal for a HVAC system is to provide proper air flow, heating, and cooling to

each room. In HVAC Industries there are so many standard organizations such as

ASHRAE, SMACNA, ACCA, Uniform Mechanical Code, International Mechanical

Code, and AMCA have been established to support the industry and encourage high

standards and achievement.

It is important that the objective criteria for system success are clearly identified

at the start of the project, because different requirements need different design

considerations.

1.3 Scope of Modern HVAC

Although there have been great advances in HVAC, there are several areas where

active research and debate continue.

Indoor air quality is one that directly affects us. In many countries of the world

there is a rapid rise in asthmatics and increasing dissatisfaction with indoor-air-quality

in buildings and planes. A significant scientific and engineering field has developed to

investigate and address these issues.



Energy conservation is an ongoing challenge to find novel ways to reduce

consumption in new and existing buildings without compromising comfort and indoor

air quality. Energy conservation requires significant cooperation between disciplines.

1.4 HVAC System

Commercial heating, ventilating, and air conditioning (HVAC) systems provide the

people working inside buildings with conditioned air so that they will have a

comfortable and safe work environment. Air quality and the condition of the air

are two very important factors. By conditioned air and good air quality, we mean

that air should be clean and odor-free and the temperature, humidity, and movement

of the air will be within certain acceptable comfort ranges.

ASHRAE, the American Society of Heating, Refrigerating and Air

Conditioning Engineers, has established standards which outline indoor comfort

conditions that are thermally acceptable to 80% or more of a commercial buildings

occupants. Generally, these comfort conditions, sometimes called the comfort zone,

are between 68F and 75F for winter and 73F to 78F during the summer. Both

these ranges are for room air at approximately 50% relative humidity and moving at a

slow speed (velocity) of 30 feet per minute or less.

An HVAC system is simply a group of components working together to move

heat to where it is wanted, or remove heat from where it is not wanted, and put it

where it is unobjectionable (the outside air).

1.4.1 Types of HVAC Systems

The basic types of HVAC systems used in commercial buildings are all-air, air and

water, all-water, and unitary. Water systems are also called hydronic systems.

Hydronic is the term used for heating and cooling with liquids. All-air systems

provide heated or cooled air to the conditioned space through a ductwork system. The

basic types of all-air duct systems are: single-zone, multizone, dual or double duct,

terminal reheat, constant air volume, variable air volume (VAV), and combination

systems.



1.4.2 Heating

Heating is one of the most important fact in the HVAC system. Heating should be

provide properly to maintain the desire temperature. There are many different types of

standard heating systems. The main components of heating systems are: Boilers,

Furnaces and Heating Coils.

1.4.3 Ventilating

Ventilating is the process of "changing" or replacing air in any space to control

temperature or remove moisture, odors, smoke, heat, dust, airborne bacteria, carbon

dioxide, and to replenish oxygen. Ventilation includes both the exchange of air to the

outside as well as circulation of air within the building. It is one of the most important

factors for maintaining acceptable indoor air quality in buildings. Methods for

ventilating a building may be divided into mechanical/forced and natural types.

Ventilation is used to remove unpleasant smells and excessive moisture, introduce

outside air, to keep interior building air circulating, and to prevent stagnation of the

interior air.

1.4.4 Air-Conditioning System

Air Conditioning within the HVAC system refers to the removal of heat from a room

or building in order to cool the air to a desired temperature. The heat transfer process

works through mediums like ice, air, water, and chemicals that are naturally cooler

than the air in the room. The air conditioning system also controls humidity levels

within the building and cools the air through a process of condensing and evaporating

a desired liquid through a series of coils, much like a refrigerator. Central air

conditioning systems that cool entire buildings can work through the same ductwork

as some central heating systems. The air is forced through the ductwork and back to

the air conditioner where it is cooled and sent back through the system. Central

cooling systems often incorporate an evaporator that collects the condensation from

the cooling coils and therefore dehumidifies the air. The resulting condensation can

then be manually removed or drained outside.



Figure 1.1 - Air-Conditioning Plant

1.4.5 Efficiency

Although most HVAC systems utilize the same ductwork for both heating and

cooling, forced-air ventilation is not necessarily the most energy efficient. By creating

zones central heating and cooling units can be better utilized through a variety of

thermostats that regulate heat and air when needed. With zones, rooms that require

heat and air can maintain comfortable while unused areas can minimize temperature

control and save energy. The most energy efficient form of heating is geothermal

heating, a method of using natural heat sources to warm buildings. Although

using HVAC systems help save some cost and energy through the use of proper air

flow and thermodynamics, the best way to maximize the efficiency of an HVAC

system is to install it in a properly designed building. Buildings need to be designed

around the potential benefits of solar energy and passive heating and cooling

opportunities. Without proper architecture, HVAC systems work harder and waste

energy.

CHAPTER TWO

HVAC System Choosing and Designing

Chapter - 2 HVAC System Choosing and Designing


2.1 Choosing an HVAC System

The purpose of an HVAC system is to provide and maintain environmental conditions

within an area called the conditioned space. The type of system selected is

determined by the mechanical designers knowledge of systems and the building

owners financial and functional goals.

It is the designers responsibility to consider the various systems and select the

one that will provide the best combination of initial cost, operating cost, performance,

and reliability based on his understanding of the owners needs and goals. In the

selection process all factors must be analyzed, but cost of installation and operation

are usually foremost.

Some of the many cost concerns include initial or installation cost, operating

and maintenance cost, and equipment replacement costs. Another cost concern that

may be overlooked by the designer is the cost associated with equipment failure. The

best situation is when designer and owner are both involved in the HVAC selection

process.

The goals of choosing of an HVAC system are-

To provide an acceptable level of occupancy comfort

To provide temperature and humidity control for process function

To maintain good indoor air quality (IAQ)

To minimize energy requirements and costs

2.1.1 HVAC System Selection Guidelines

Each of the following issues should be taken into consideration each time an HVAC

system is selected.

1) Financial factors

Initial cost

Operating costs

Maintenance and repair cost

Equipment replacement or upgrading cost

Equipment failure cost

Return on investment (ROI)

Energy costs



2) Building conditions

New or existing building or space

Location

Orientation

Architecture

Climate and shading

Configuration

Construction

Codes and standards

3) Usage

Occupancy

Process equipment

4) Energy availability

Types

Reliability

5) Control scheme

Zone control

Individual control

2.2 Choosing an Air-Conditioning System

The factors or parameters that influence system choice can conveniently be divided

into the following groups:

2.2.1 Building Design

The design of the building has a major influence on system choice.

2.2.2 Location Issues

The building location determines the weather conditions that will affect the building

and its occupants. For the specific location we will need to consider factors like:

site conditions

peak summer cooling conditions

summer humidity

peak winter heating conditions



wind speeds

sunshine hours

typical snow accumulation depths

The building location and, at times, the client, will determine what national, local, and

facility specific codes (Building code, Fire code, Energy code) must be followed.

Typically, the designer must follow the local codes.

2.2.3 Utilities: Availability and Cost

The choice of system can be heavily influenced by available utilities and their costs to

supply and use. So, if chilled water is available from the adjacent building, it would

probably be cost advantageous to use it, rather than install new unitary refrigerant-

based units in the new building.

2.2.4 Indoor Requirements and Loads

The location effects and indoor requirements provide all the necessary information for

load calculation for the systems.

The thermal and moisture loads

Outside ventilation air

Zoning

2.2.5 Client Issues

The designer has to consider the clients requirements both for construction and for

in-use costs. The client may wish to finance a very sophisticated and more expensive

system to achieve superior performance, or to reduce in-use costs. In addition to cost

structures, the availability of maintenance staff must be considered. A building at a

very remote site should have simple, reliable systems, unless very competent and

well-supported maintenance staff will be available.

2.2.6 System Choice

While all the above factors are considered when choosing a system, the first step in

making a choice is to calculate the system loads and establish the number and size of

the zones. Typically, after some systems have been eliminated for specific reasons,

one needs to do a point-by-point comparison to make a final choice.



2.3 Unitary System Selection Guidelines

Unitary systems are selected when it is decided that a central HVAC system is too

large or too expensive for a particular project, or a combination system is needed for

certain areas or zones to supplement the central system.

2.3.1 Factors to Consider When Selecting Unitary Systems

i. Control of Temperature and Airflow

ii. One Manufacturer is Responsible for the Final Unit

iii. Maintenance and Operation

iv. Costs and Energy Efficiency

2.4 HVAC Design

Best-in-class HVAC system design and analysis are critical elements of creating the

optimal building environment. Given the level of control and the performance

demands of todays sophisticated HVAC systems, seemingly incremental efficiencies

result in significant reductions of resource requirements. Accurate analysis and

specifications translate into substantial savings and optimal performance for building

owners. Conducting comprehensive load analyses, considering air supply

requirements, weather conditions, determining optimum HVAC system, piping and

duct configurations, and then applying those considerations to specifications are all

critical to high performance building design.

Pharmaceutical manufacturing is generally conducted in environments that are

cleaner and are carefully controlled at a required temperature, humidity and pressure.

The HVAC system assumes a large part of the responsibility in maintaining these

clean environments.

2.4.1 Design of an Air Handling Unit

Choosing of an Air Handling System is very important for a pharmaceutical industry.

Air Handling Units are designed to create a symbiosis of heat, ventilation and air

filtration. The result is a perfectly balanced environment for people and industry.

2.4.1.1 Sub-Systems of AHU

A conventional Air Handling System has 4 sub-systems:



1. Air handling of the incoming (fresh) air, elimination of coarse contaminants

and protection from frost if necessary. In the case of air re-circulation, the

fresh air is also called make-up air.

2. Central air handling unit (AHU), where the air will be conditioned (heated,

cooled, humidified or de-humidified and filtered), and where fresh air and re-

circulated air, if any, (indicated here by the dotted line) will be mixed.

3. Air handling in the rooms under consideration (pressure differential system,

additional filtration, air distribution)

4. Air exhaust system (filtration)

Figure 2.1 - Sub-systems of AHU

2.4.1.2 Air Flow Patterns

There are 2 ways to supply air to a room: Turbulent air flow and Uni-

directional flow, often called laminar flow

The air speed in the uni-directional flow is defined by the WHO at: 0.45 m/s

for horizontal units and 0.30 m/s for vertical units (most commonly used)

For the air exhaust, in case of a vertical unit, a low return is more favorable, as

the air is better distributed in the room

Objects in the room can significantly disturb the flow of air, and even block it,

so that there might be pockets without air circulation.



(a)

(b)

Figure 2.2 - (a) Turbulent Air Flow, (b)Uni-directional or Laminar Air

Flow

Filtered air entering a production room or covering a process can be meet

GMP aspects and Economical aspects

Figure shows an HVAC installation feeding 3 rooms, each one with terminal

filters, all terminal filters protected by a remote pre-filter. Room 1 has a

turbulent air flow, with low level exhaust. Room 2 has a uni-directional air

flow, over the largest part of the surface, hence the large number of filters,

with low level air returns.

Due to the high cost of the ventilation in class A areas, the tendency is to keep

these areas as small as possible. Room 3 has a turbulent air flow, with ceiling

exhaust.

Figure 2.3 - Room 1, 2 & 3 with different air flow patterns and exhaust

systems

Uni-directional (laminar) flow units exist mostly as vertical, but also as

horizontal, units.

In some cases, the units can be integrated into the ceiling of a room and also

connected to the central air conditioning system.

Laminar flow units are comparatively expensive. Surfaces covered by them

should be reduced to a minimum. Only the product in a critical production



phase, and not the personnel, should be under laminar flow (aseptic filling,

sterile blending, etc.).

2.4.1.3 Filters Positions

The filtered air entering a production room can be coming from:

an air-handling unit, equipped with pre-filtration and the main (HEPA) filter,

but at some distance from that room;

an air-handling unit, equipped with pre-filtration in the AHU, and an

additional filter (HEPA) situated immediately on the air outlet.

the terminal positioning is more expensive; provides a better protection; is the

preferred method in clean room classes with high requirements.

Figure 2.4 - AHU mounted final filter

Figure 2.5 - Filter in terminal position

Filters can be in different positions, when one considers the central AHU and

the rooms.

The figure shows an HVAC installation feeding 3 rooms, each one with

terminal filters, all filters protected by a remote pre-filter.

Room 1 has a turbulent air flow, with low level exhaust. Room 2 has a uni-

directional (laminar) air flow over the largest part of the surface, hence the

large number of filters. Room 3 has a turbulent air flow, with ceiling exhaust.



Figure 2.6 - HVAC installation feeding 3 rooms

The figure shows an HVAC installation feeding two rooms, each one without

terminal filters, but with remote final filters protected by a pre-filter.

Room 1 has a turbulentair flow, with low level exhaust. Room 2 has a

turbulent air flow, with ceiling exhaust.

If there is no filter in terminal position, it should be ascertained that there are

no elements between the main filter and the air outlets which could add

contamination.

Figure 2.7 - HVAC installation feeding 2 rooms

2.4.1.4 Air Circulation System

2.4.1.4.1 Air Re-Circulation

Re-circulated air must be filtered, at an efficiency rate which is such that

cross-contamination can be excluded.

In case of re-circulation, every possible measure of protection must be taken to

ensure that the air coming from a production unit and loaded with product

particles does not flow to other production units, thereby contaminating them.

It makes sense to re-circulate the air for reasons of energy conservation, but

there can be a contradiction between pharmaceutical requirements and energy

conservation.



There are also cases, in which air re-circulation is prohibited, for example if

solvents are used or cytotoxic products are manufactured.

2.4.1.4.2 Ventilation with 100% fresh air (no air re-circulation)

A typical 100% fresh air setup, where a central unit distributes the fresh,

treated air to different production rooms.

The exhaust air is collected in a central duct, treated (filtered or washed) and

eliminated. The degree of exhaust air filtration will depend on contaminants in

the exhaust air and also on environmental regulations.

Figure 2.8 - Ventilation with 100% fresh air (no air re-circulation)

2.4.1.4.3 Ventilation with re-circulated air with make-up air

A typical re-circulated air setup, where a central unit distributes a mixture of

fresh and re-circulated air to different production rooms.

A part of the exhaust air is collected in a central duct, treated (filtered) and

exhausted. The rest is re-circulated (dotted line).

With control dampers, the proportions of fresh and re-circulated air can be

adjusted.

Figure 2.9 - Ventilation with re-circulated air with make-up air

CHAPTER THREE

Zoning Design, Central

Plants and Hydronic

Systems

Chapter - 3 Zoning Design, Central Plants and Hydronic Systems


3.1 Zone

To maximize thermal comfort, systems can be designed to provide independent

control in the different spaces, based on their users and requirements. Each space or

group of spaces that has an independent control is called a zone.

A zone is a part of a building whose HVAC system is controlled by a single

sensor. The single sensor is usually, but not always, a thermostat. Either directly or

indirectly, a thermostat controls the temperature at its location.

3.1.1 Zoning Design

There are several types of zones. These zones are differentiated based on what is to be

controlled, and the variability of what is to be controlled. The most common control

parameters are: thermal, humidity, ventilation, operating periods, freeze protection,

pressure and importance.

The most common reason for needing zones is variation in thermal loads.

Consider the simple building floor plan shown in Figure 3.1. Let us assume it has the

following characteristics:

Well-insulated

A multi-story building, identical plan on every floor

Provided with significant areas of window for all exterior spaces

Low loads due to people and equipment in all spaces

Located in the northern hemisphere

The designers objective is to use zones to keep all spaces at the set-point

temperature.

Figure 3.1 - Building Plan



Zones are designed on the basis of some factors:

Zoning Design Considerations

Interior and Roof Zones

Thermal Variation

Ventilation with Outside Air

Time of Operation

Humidity

Pressure

Zoning Problems

3.1.2 Controlling the Zone

The most common zone control is the thermostat. It should be placed where it is most

representative of the occupants thermal experience. A thermostat does its best to

keep a constant temperature where it is.

3.2 Single Zone Air Handlers

The single zone air handler, or air-handling unit, often abbreviated to AHU. The air

handler draws in and mixes outside air with air that is being recirculated, or returned

from the building, called return air. Once the outside air and the return air are mixed,

the unit conditions the mixed air, blows the conditioned air into the space and

exhausts any excess air to outside, using the return-air fan.

3.2.1 Examples of Buildings with Single-zone Package Air-Conditioning Units

Building A: This unit has only an electrical supply. This single electrical supply

provides all the power for heating, cooling, humidifying, and for driving the fans.

Building B: This unit has the electrical supply for cooling, humidifying, and for

driving the fans, while the gas line, shown as gas supply, provides heating.

Building C: This unit has the electrical supply for cooling, humidifying, and for

driving the fans. It also has supply and return hot-water pipes coming from a boiler

room in another building. The unit contains a hot-water heating coil and control valve,

which together take as much heat as needed from the hot water supply system.

Building D: In the same way, there may be a central chiller plant that produces cold

water at 42F 48F, called chilled water. This chilled water is piped around the



building, or buildings, to provide the air-handling units with cooling. Like the heating

coil and control valve in Building C, there will be a cooling coil and control valve in

each unit, to provide the cooling and dehumidification.

Figure 3.2 - Single Zone Rooftop Air-Conditioning Unit, Energy Supplies

3.2.2 Air-Handling Unit Components

Components of the unit can include: inlet louver screen, the parallel blade damper,

opposed blade damper, the relief air damper, actuator, the mixed temperature sensor,

filter, heating coil, cooling coil, humidifier, fan, and return fan.

Figure 3.3 - Air-Conditioning System: Single-Zone Air Handler



3.2.2.1 Refrigeration Equipment

The vapor compression refrigeration cycle is generally the basis of mechanical

refrigeration. The vapor compression refrigeration system comprises four

components: compressor, condenser, expansion valve, and evaporator. This system

can be used directly, to provide cooling to, typically, a local coil.

Figure 3.4 - Basic Vapor Compression Refrigeration Cycle

3.2.2.2 System Performance Requirements

Before choosing a system, we need an understanding of the types of loads we want

the system to manage. Summer cooling loads will be the main determinant of the

choice of unit to determine the summer load: outside design temperature; outside

design humidity; inside design temperature and humidity; inside generation of heat

and moisture; ventilation requirements.

3.2.2.3 Rooftop Units

In a typical rooftop unit, the return air is drawn up into the base of the unit and the

supply air is blown vertically down from the bottom of the unit into the space below.

As an alternative, the ducts can come out of the end of the unit to run across the roof

before entering the building. Choice factors to choose a rooftop unit: inside and

outside design temperatures, required airflow, mixed air temperature, and the required

sensible and latent cooling loads.



Figure 3.5 - Rooftop Unit

3.2.2.4 Split Systems

In the split system, the compressor/condenser part of the refrigeration system separate

from the evaporator coil and connected by the refrigerant lines to the air system,

which includes the evaporator.

Figure 3.6 - Split System

3.3 Multiple Zone Air Systems

In many buildings, the unit must serve several zones, and each zone has its own

varying load. To maintain temperature control, each zone has an individual thermostat

that controls the volume and/or temperature of the air coming into the zone.

A system thermodynamically similar to the dual-duct system, the multizone

system features a different layout. The multizone system is not as energy efficient as

the VAV system, and requires a separate duct to each zone. However, the multizone

system has the advantage of requiring no maintenance outside the mechanical room,

except for the zone temperature-sensors and associated cable.

All-air systems advantages:

Centrally located equipment



Least infringement on conditioned floor space

Greatest potential for the use of an economizer cycle

Zoning flexibility and choice

Full design freedom

Generally good humidity control

All-air systems disadvantages:

Increased space requirements

Construction dust

Closer coordination required

Figure 3.7 - Mixing at the Air Conditioning Unit in a Multizone System

3.3.1 Three Deck, Multizone System

The more modern introduction of the third, neutral duct to the multizone system,

avoids the conflict of concurrent heating and cooling.

3.3.2 Dual Path, Outside Air System

This system could be used to reduce the problem with excess moisture in the air that

arises in warm/hot, humid climates.

3.3.3 Single-Duct, Zoned Reheat, Constant Volume Systems

Reheat is the simplest system, known for both its reliability and the down side, its

high energy wastage. The reheat system permits zone control by reheating the cool

airflow to the temperature required for a particular zone.



Figure 3.8 - Reheat System

3.3.4 Single-Duct, Variable Air Volume Systems

The variable air volume system is designed with a volume control damper, controlled

by the zone thermostat, in each zone. VAV system adjusts for varying cooling loads

in different zones by individually throttling the supply air volume to each zone.

Figure 3.9 - Variable Air Volume System

3.3.5 Dual-Duct, Variable Air Volume System

A modification of the dual-duct system, this system uses variable volume dual-duct

boxes to provide the thermal efficiency of the VAV system, while maintaining higher

air flows, and thus better room air circulation when heating is required.

3.3.6 By Pass Box Systems

A variation on the VAV system, the bypass system, is suitable for providing good

control in smaller systems and for constant flow over a direct-expansion cooling coil.

Designers must be cautious to ensure that bypassed air goes straight back to the air

conditioning unit, but it is generally a simple system to design.



Figure 3.10 - By-Pass Boxes on Each Zone

3.3.7 Constant Volume Dual-Duct, All-Air Systems

In a dual-duct system, cooling and heating coils are placed in separate ducts, and the

hot and cold air flow streams are mixed, as needed, for temperature control within

each zone. A very attractive feature of the dual-duct system is that there are no reheat

coils near the zones, so the problems of leaking hot water coils is avoided.

Figure 3.11 - Dual-Duct System, Double Line Diagram

3.4 Central Plants

Central plants include boilers, producing steam or hot water, and chillers, producing

chilled water. These pieces of equipment can satisfy the heating and cooling

requirements for a complete building. In a central plant, the boilers and chillers are

located in a single space in the building, and their output is piped to all the various air-

conditioning units and systems in the building. Their initial cost is often higher than



packaged units and they require installation floor area as well as space through the

buildings for distribution pipes.

The main items of equipment found in central plants are:

Boilers are pressure vessels and their installation and operation are strictly

prescribed by codes.

Chillers come in a huge range of sizes and types. Their particular

requirements for chilled water piping and specialized control. The job of the

chiller is to remove heat from the chilled water and reject it to the condenser.

Cooling towers are devices used to cool water by evaporation. Water is

sprayed or dripped over material with a large surface area, while outdoor air is

drawn through.

3.4.1 Boilers

Boilers are pressure vessels used to produce steam or hot water. The critical design

factor for boilers is pressure. A low-pressure steam boiler operates at a pressure of no

more than 15 psig. Low-pressure hot water boilers are allowed up to 160 psig.

3.4.1.1 Boiler Components

Boilers have two sections: The combustion section is the space where the fuel air

mixture burns; the second section of the boiler is the heat transfer section. In all

boilers there is a need to modulate the heat input.

In steam systems, there is a constant loss of water in the condensate return

system. To prevent problems with solids build-up in the boiler and distribution pipe

corrosion, continuous high quality water treatment is required.

Figure 3.12 - Hot Water Heating System with Two Boilers



3.4.2 Water Chillers

The chiller includes an evaporator or liquid cooler, a condenser, and a compressor.

The main energy-using components of chiller plant are the motors that drive the

compressors, chilled water pumps, condenser water pumps, air-cooled condenser fans,

and cooling tower fans.

The water that flows through the evaporator coil gives up heat, and becomes

cooler. The cooled water is referred to as chilled water. The water that flows

through the condenser, called the condenser water, becomes warmer and is piped

away to a cooling tower to be cooled before returning to the condenser to be warmed

again.

The two categories of water chillers used in HVAC systems are:

i. Mechanical chiller

ii. Absorption chiller

Figure 3.13 - Water Chiller with Water Cooled Condenser

Variable chilled water flow arrangement is shown in the figure. In the diagram, at full

load, both chillers and pumps are running, and the valves in the coil circuits are fully

open. As the load decreases, the temperature sensors, in front of each coil, start to

close their valve, restricting the flow through the coil.



Figure 3.14 - Two Chiller Piping with Constant Chiller Flow

3.4.3 Centrifugal Water Chillers

The centrifugal refrigeration machine was the first practical method of air

conditioning large spaces. The heart of a centrifugal water chiller is the centrifugal

compressor.

Figure 3.15 - Centrifugal Mechanical Chiller

3.4.3.1 Central Plant Water Chiller Optimization

To determine if the central plant can be optimized, the first step is to conduct an

energy survey and testing of the systems operating performance. The second step is



to consider the options. The third step to any proposed retrofit is to consider the

consequences of the retrofit before starting the project.

The following are some ways to optimize the chiller plant:

Select Proper Air Quantities and Heat Transfer Surfaces for the Cooling Coils

Raise the Evaporator Temperature

Lower Condenser Water Temperature

Optimize Chillers in Series

Optimize Chillers in Parallel

Install Water-side Economizers

3.4.4 Cooling Towers

Cooling towers are a particular type of big evaporative cooler. In the cooling tower,

warm water is exposed to a flow of air, causing evaporation and therefore, cooling of

the water. The psychrometric chart can be used to illustrate the workings of the

cooling tower.

Figure 3.16 - Typical Natural-Draft

Open Cooling Tower

Figure 3.17 - Induced Draft, Closed

Circuit Cooling Tower

3.5 Hydronic Systems

In some buildings, these systems will use low-pressure steam instead of hot water for

heating. The performance is generally similar to hot water systems, with higher

outputs due to the higher temperature of the steam.



Hydronic systems are most commonly used where high and variable sensible

heating and/or cooling loads occur. These are typically

Perimeter zones, with high solar heat gains or

Perimeter areas in cooler to cold climates where there are substantial

perimeters heat losses

Hydronic systems advantages:

i. Noise reduction virtually silent operation

ii. Economy due to limited operational costs large amounts of heat from small

local equipment

iii. Economy due to limited first costs pipes are small compared to ducts for

the same heat transfer around a building

iv. Energy efficiency low energy consumption at low load

Hydronic systems disadvantages:

i. Ventilation provision of outside air for ventilation is either absent or poor

ii. System failure danger from freezing and from leaks

iii. Humidity control is either absent or generally poor

3.5.1 Natural Convection and Low Temperature Radiation Heating Systems

The very simplest water heating systems consist of pipes with hot water flowing

through them. The output from a bare pipe is generally too low to be effective, so an

extended surface is used to dissipate more heat. The radiator emits heat by both

radiation and convection. These water heaters can all be controlled by varying the

water flow or by varying the water supply temperature.



Figure 3.18 - Wall-Mounted Single and Double Panel Radiators

3.5.2 Panel Heating and Cooling

Radiant floors use the floor surface for heating. Ceilings can also be used for heating

and/or cooling. The system has the advantage of taking up no floor or wall space and

it collects no more dirt than a normal ceiling.

Figure 3.19 - Concrete Radiant Floor

3.5.3 Fan Coils

Fan coils can be used for just heating or for both heating and cooling. When the fan-

coil is used for heating, the hot water normally runs through the unit continuously.

When the thermostat switches the fan on, full output is achieved. Some units are

provided with two or three speed controls for the fan, allowing adjustment in output

of heat and generated noise. Types of fan coils include: Hot-water fan coils,

changeover systems, and four-pipe systems.



Figure 3.20 - Typical Fan-Coil Unit

3.5.4 Fan Curves

A fan curve shows the performance of a fan at various static pressures and volumes of

airflow. At the top left of the curve is the block tight static pressure condition at

maximum static pressure and zero airflow.

3.5.5 Two Pipe Induction Systems

The two-pipe induction system uses ventilation air at medium pressure to entrain

room air across a coil that either heats or cools. The units are typically installed under

a window, and when the air system is turned off, the unit will provide some heat by

natural convection if hot water is flowing through the coil.

Figure 3.21 - Induction Unit



3.5.6 Water Source Heat Pumps

Water source heat pumps are refrigeration units that can either pump heat from water

into the zone or extract heat from the zone and reject it into water. This ability finds

two particular uses in building air conditioning:

a) The use of heat from the ground

b) The transfer of heat around a building

3.6 Hydronic System Architecture

The basic layout options for heating and cooling piping arrangements that distribute

water or steam, hydronic circuits. In each case, a flow of water or steam is distributed

from a either a central boiler or a chiller, the refrigeration equipment used to produce

chilled water, to the hydronic circuits.

3.6.1 Steam Systems

Principal ideas of this section include: how steam is used; its behavior as a gas and

how it condenses as it gives up its latent heat; how the resultant condensate is drained

out of the steam pipes by traps and then returned to the boiler, to be boiled into steam

again.

Figure 3.22 - Steam System

3.6.2 Water Systems

In the water systems, we need economical direct arrangement and the more costly, but

largely self-balancing, reverse-return piping arrangement. The advantages of water

over steam include the fact that water is safer and more controllable than steam.

Water System Design Issues are: Pipe Construction and Pipe Distribution.



3.6.3 Hot Water Systems

Within buildings, hot water is the fluid that is most commonly used for heat

distribution. The amount of heat that is transferred is proportional to the temperature

difference between supply and return.

3.6.4 Chilled Water Systems

Because chilled water systems need constant water flow through the chiller

evaporator, the economies of variable flow can be achieved through decoupled and

distributed piping arrangements.

Figure 3.23 - Chiller System with Decoupled Flows

3.6.5 Condenser Water System

Condenser water is water that flows through the condenser of a chiller to cool the

refrigerant. Condenser water from a chiller typically leaves the chiller at 95F and

returns from the cooling tower at 85F or cooler.

Figure 3.24 - Evaporative Cooling Tower

CHAPTER FOUR

Control Systems and

Thermal Comforts

Chapter - 4 Control Systems and Thermal Comforts


4.1 HVAC Control Systems

The purpose of an HVAC automatic control system is to start, stop or regulate the

flow of air, water or steam and to provide stable operation of the system by

maintaining the desired temperature, humidity and pressure. The automatic control

system is a group of components, each with a definite function designed to interact

with the other components so that the system is self-regulating. HVAC control

systems are classified according to the source of power used for the operation of the

various components. Whether the controls are a factory package or built-up on site,

well-designed controls are a critical part of any HVAC system.

The classifications and power sources are:

a) Pneumatic Systems:

Compressed air.

b) Electric Systems:

Low voltage electricity (normally 24 Volts)

Line voltage electricity (normally 110 to 220 Volts)

c) Electronic Systems (DDC):

Low voltage electricity (normally 5 to 15 Volts).

d) Electric- or Electronic-to-Pneumatic Systems:

Electricity and compressed air.

4.2 Control Loops

Information flows in a circle from the sensor measuring the controlled variable to the

controller where the current value of the controlled variable is compared to the

desired value or set point.

Figure 4.1 - Diagram of Control Loop



4.3 Control Modes

All controllers are designed to take action in the form of an output signal to the

controlled device. The output signal is a function of the error signal, which is the

difference between the control point and the setpoint. The type of action the controller

takes is called the control mode or control logic, of which there are three basic types:

i. Two-position control

ii. Floating control

iii. Modulating control

4.4 Control Types

4.4.1 Self-powered Controls

Self-powered Controls require no external power. Various radiator valves and ceiling

VAV diffusers have self-powered temperature controls.

4.4.2 Electric Controls

Electric Controls are powered by electricity.

On/off Electric Control

Modulating Electric Controls.

4.4.3 Pneumatic Controls

Pneumatic controls, which use compressed air as the power source, are very simple

and inherently analog, making them ideal for controlling temperature, humidity, and

pressure.

4.4.4 Electronic Controls

Electronic Controls, use varying voltages and currents in semiconductors to provide

modulating controls. They have never found great acceptance in the HVAC industry,

since DDC offered much more usability at a much lower price.

4.4.5 Direct Digital Controls, DDC

Direct Digital Controls, DDC, are controls operated by one, or more, small computer

processors. The computer processor uses a software program of instructions to make



decisions based on the available input information. The processor operates only with

digital signals and has a variety of built-in interface components so that it can receive

information and output control signals.

Figure 4.2 - DDC Control Schematic

4.4.5.1 Benefits of DDC:

Direct Control, Precise Control, Dead Band and Control Sequence, Schedule

Changes, Flexibility

4.5 Control System Components

4.5.1 Controllers

A controller is a proportioning device designed to control dampers or valves to

maintain temperature, humidity, or pressure. A controller may be direct acting or

reverse acting. Types of controllers: thermostats, humidistats for humidity,

pressurestats for pressure, master controllers to control submaster controllers, and

receiver-controllers.

4.5.1.1 Single Pressure Thermostat

A single pressure thermostat may be a one-pipe, bleed-type or a two pipe, relay-type

controller. The main air is introduced through a restrictor into the branch line between

the thermostat and the controlled device.

4.5.1.2 Dead Band Thermostat

A dead band thermostat is a two-pipe controller that operates in the same manner as a

single pressure, single temperature thermostat. Its used for energy conservation when



a temperature span or dead band is required between the heating and cooling

setpoints.

4.5.1.3 Dual Pressure Thermostat

The summer/winter system provides for the seasonal requirements of either cooling or

heating and, depending on the season, either chilled water or hot water is supplied to

the water coil in the air handing unit.

4.5.1.4 Humidistat

Humidistats are similar in appearance to thermostats; however, instead of using a

bimetal strip as the sensor, humidity is sensed by a hygroscopic, or water absorbing,

material such as human hair, nylon, silk, wood or leather.

4.5.1.5 Master/Submaster Controller

A master controller is one which transmits its output signal to another controller. The

second controller is called the submaster. The submasters setpoint will change as the

signal from the master controller changes. This is a reset type of control.

4.5.1.6 Receiver-controller and Transmitter

The receiver-controller and transmitter is the controlling device used most often in

present day pneumatic HVAC control systems. The receiver-controller, like the other

controllers, receives a signal from a sensor and then varies its branch output pressure

to the controlled device. The sensing device for receiver-controllers is the transmitter.

Transmitters are one-pipe, direct acting, bleed-type devices which use a restrictor in

the supply line to help maintain the proper volume of compressed air between the

transmitter and the receiver-controller.

4.6 Energy Conservation

The objective of energy conservation is to use less energy. This is accomplished by

various methods, including recycling energy where useful. Energy conservation

should be part of the entire life cycle of a building: it should be a consideration during

the initial conception of a building, through its construction, during the operation and

maintenance of the building throughout its life, and even in deconstruction. Energy



efficient the system as initially designed and installed the energy efficiency will

degrade unless it is operated correctly and deliberately maintained.

4.7 Parameters to Control

4.7.1 Importance of Humidity Control

1) Stability and longer shelf life: Humidity control is important for the stability

and longer shelf life of products. Controlled humidity decreases the

decomposition rate of drugs. It will also help to maintain the physical stability

of dosage form. As a result the shelf life of the dosage form will increase.

2) Comfort requirement: Humidity is a comfort requirement. Suitable moisture

level is required to offer a comfortable working environment for the operators.

3) To inhibit microbial growth: Above 60% RH promotes bacterial growth. So

relative Humidity should be maintained < 55% to inhibit microbial growth in

various production areas.

4) To facilitate various processes: Less humidity makes some problems to

disinfect an area. On the other hand less humidity is required for drying

process. Materials can be effectively dried in controlled humidity.

5) Storage of EHGCS & water sensitive materials: Ideal storage condition of

EHGCS is 45% - 60% RH. At low humidity the capsules become brittle and at

high humidity they become flaccid and lose their shape. Moisture sensitive

materials should also be stored in lower humidity.

6) Production and packing of various dosage forms: Humidity control is

essential for the manufacturing of various dosage forms.

Capsule preparation: RH should be maintained 45% - 55% for proper

encapsulation. Otherwise capsules will absorb moisture and become soft.

Dry syrup preparation: < 50% RH is required for dry syrup

preparation. Lump formation is possible due to over moisture.

Hygroscopic tablet preparation: Controlled humidity is required for the

granulation, compression, coating and packing of hygroscopic tablets.

Over moisture may dissolve the materials.

7) Maintenance of equipment: Humidity control is essential to maintain

sophisticated QC instruments.



4.7.2 Importance of Temperature Control

1) Stability and longer shelf life: Temperature control is important for the

stability and longer shelf life of product. Controlled temperature decreases the

decomposition rate of drugs. It will also help to maintain the physical stability

of dosage form. As a result the shelf life of the dosage form will increase.

2) Comfort requirement: Temperature is a comfort requirement. Suitable

temperature is required to offer a comfortable working environment for the

operators.

3) To inhibit microbial growth: Microbial growth is accelerated by the

optimum temperature. 370c temperature promotes the bacterial growth.

Microbial growth can be inhibited by controlling temperature.

4) Storage of EHGCS & thermo labile materials: Ideal storage condition of

EHGCS is 25 - 300c. They lose their shape at high temperature. Moisture

sensitive materials should also be stored in lower temperature.

5) Production and packing of various dosage forms: Temperature control is

essential for the manufacturing of various dosage forms.

4.7.3 Importance of Dust Particle Control

1) Purity of product

2) Patients safety

3) To inhibit microbial load

4) Production and packing of various dosage forms

4.8 Thermal Comfort

Thermal comfort is primarily controlled by a buildings heating, ventilating and air-

conditioning systems, though the architectural design of the building may also have

significant influences on thermal comfort. Standard 55 defines thermal comfort as

that condition of mind which expresses satisfaction with the thermal environment

and is assessed by subjective evaluation.

4.8.1 Factors Influencing Thermal Comfort

There are seven factors which are influencing the thermal comfort. They are:



Personal

1. Activity level

2. Clothing

Individual Characteristics

3. Expectation

Environmental Conditions and Architectural Effects

4. Air temperature

5. Radiant temperature

6. Humidity

7. Air speed

4.8.1.1 Activity Level

The human body continuously produces heat through a process call metabolism.

This heat must be emitted from the body to maintain a fairly constant core

temperature, and ideally, a comfortable skin temperature. As activity increases, from

sitting to walking to running, so the metabolic heat produced increases.

4.8.1.2 Clothing

In occupied spaces, clothing acts as an insulator, slowing the heat loss from the body.

To predict thermal comfort we must have an idea of the clothing that will be worn by

the occupants. Due to the large variety of materials, weights, and weave of fabrics,

clothing estimates are just rough estimates.

4.8.1.3 Occupants Expectations

Peoples expectations affect their perception of comfort in a building. Standard 55

recognizes that the expectations for thermal comfort are significantly different in

buildings where the occupants control opening windows, as compared to a

mechanically cooled building.

4.8.1.4 Air Temperature

When we are referring to air temperature in the context of thermal comfort, we are

talking about the temperature in the space where the person is located.



4.8.1.5 Radiant Temperature

Radiant heat is heat that is transmitted from a hotter body to a cooler body with no

effect on the intervening space. For internal spaces, where the temperature of the

walls, floor and ceiling are almost the same as the air temperature, the radiant

temperature will be constant in all directions and virtually the same as the air

temperature.

4.8.1.6 Humidity

Low humidity: For some people, low humidity can cause specific problems,

like dry skin, dry eyes and static electricity. However, low humidity does not

generally cause thermal discomfort.

High humidity: Standard 55 does define the maximum humidity ratio for

comfort at 0.012 lb/lb. Since it is equivalent to 100% relative humidity at

62F.

4.8.1.7 Air Speed

The higher the air speed over a persons body, the greater the cooling effect.

4.9 Heat Flow and Heat Recovery

4.9.1 Heat Flow

Heat is energy in the form of molecules in motion. Heat flows from a warmer

substance to a cooler substance. Heat energy flows downhill. Heat does not rise,

heated air rises.

4.9.1.1 Heat Transfer

Heat naturally flows from a higher energy level to a lower energy level. When there is

a temperature difference between two substances, heat transfer will occur. The greater

the temperature difference, the greater the heat transfer.

4.9.1.2 Types of Heat Transfer

The three types of heat transfer are conduction, convection and radiation.



4.9.1.2.1 Conduction

Conduction heat transfer is heat energy traveling from one molecule to another. A

heat exchanger in an HVAC system uses conduction to transfer heat.

4.9.1.2.2 Convection

Heat transfer by convection is when some substance that is readily movable such as

air, water, steam, or refrigerant moves heat from one location to another. An HVAC

system uses convection in the form of air, water, steam and refrigerants in ducts and

piping to convey heat energy to various parts of the system.

4.9.1.2.3 Radiation

Heat transferred by radiation travels through space without heating the space.

Radiation or radiant heat does not transfer the actual temperature value.

4.9.1.3 Heat Transfer Equations

1) Air System - Sensible Heat Transfer Equation

Btuh = cfm 1.08 TD

2) Air Syatems - Total Heat Transfer Equation

Btuh = cfm 4.5 h

3) Water System - Heat Transfer Equation

Btuh = gpm 500 TD

4.9.2 Heat Recovery

The objective of heat-recovery systems is to reduce the energy consumption and cost

of operating a building by transferring heat between two fluids, such as exhaust air

and outside air. In many cases, the proper application of heat-recovery systems can

result in reduced energy consumption and lower energy bills, while adding little or no

additional cost to building maintenance or operations.

4.9.2.1 Heat Recovery Systems

There are three basic types of heat recovery systems: comfort- to-comfort, process-to-

comfort, and process-to-process.



4.9.2.1.1 Comfort- to-Comfort Heat Recovery Systems

Comfort-to-comfort systems are typically used in HVAC applications. These heat

recovery systems capture a buildings exhaust air and reuse the energy in that waste

heat to precondition the outside air coming into the building. In comfort-to-comfort

applications, the energy recovery process is reversible. To determine the amount of

heat transferred, use the sensible heat transfer equation.

Btuh = cfm 1.08 T

4.9.2.1.2 Process-to-Comfort Heat Recovery Systems

Process-to-comfort systems are generally sensible heat recovery only. Therefore, they

are used only during the spring, fall, and winter month but there is no heat recovery

during the summer months.

4.9.2.1.3 Process-to-Process Heat Recovery Systems

Process-to-process systems also perform sensible heat recovery only, usually full

recovery, but in some cases, partial recovery can be performed if circumstances

dictate.

CHAPTER FIVE

Future Trend to HVAC

Chapter 5 Future Trend to HVAC


5.1 Future Trend to HVAC

Modern building and HVAC systems are required to be more energy efficient while

adhering to an ever-increasing demand for better indoor air quality and performance.

Economical consideration and environmental issues also need to be taken into

account. These factors, as well as an increase in design liability and requirement to

complete designs quickly, have placed unprecedented pressure on designer.

Computers are seen as an important design tool that can reduce some of the strain.

5.2 Future Revolution in HVAC Design

Contemporary practice in heating, ventilation, and air conditioning (HVAC) is

inadequate to fulfill the stringent demands of the 21st century. It is deficient in

comfort, ventilation, indoor air quality, fire safety, energy efficiency, and resistance to

terrorism.

For several decades now, HVAC designers have known that they must make

their systems more energy efficient, but combining efficiency with high standards of

comfort and health has proven to be an elusive goal. It may seem that performance

compromises are inescapable, but that is not true. Present problems stem from

continuing along an evolutionary design path that took a wrong turn in the past.

In this series of two articles, we will recognize flawed premises in present

HVAC practice, make a major change in HVAC design, and eliminate the defects of

HVAC equipment. We will find that it is possible to satisfy all the requirements that

HVAC must meet during this century.

5.3 Logic of the HVAC Revolution

The accumulation of unsolved problems in contemporary HVAC requires us to stop

and take a fresh look. While we exploit the lessons of past experience, we will

abandon assumptions that are no longer relevant and change practices that fail to

achieve optimum performance.

HVAC today uses two broad approaches. For compartmentalized buildings, the

dominant design approach is using centralized air handling systems that serve

multiple zones. For smaller buildings, and for individual spaces whose conditioning

requirements do not match the rest of the building, the dominant approach is using

single-zone systems.



The first step toward optimum HVAC is recognizing that multiple-zone air

handling systems inherently cannot optimize all HVAC functions, nor can they

operate with a high level of energy efficiency unless they seriously degrade the

comfort and health functions of the systems. This is a theoretical limitation, not just a

practical one. Therefore, multiple-zone HVAC systems must be abandoned.

5.4 Optimized Function HVAC Design

HVAC for this century must become fully optimized. Each comfort, health, and safety

function required for each zone in the facility must be executed perfectly, and no

energy waste is permitted. This criterion is entirely achievable by a disciplined design

process that focuses on the system functions.

This is the design sequence for optimized-function HVAC:

i. Define all the conditioning functions that are needed for each application in

the facility.

ii. Define the spatial zones that correspond to each function.

iii. For each zone, identify the kinds of equipment that can fulfill each function

optimally.

iv. Consolidate the equipment for each zone without compromising optimum

performance.

v. Provide optimum control for all operating conditions.

5.5 Central Plant Equipment in Optimized Systems

In the strictest sense, centralized plants especially cooling plants cannot optimize

energy efficiency. A chiller must make water cold enough to serve the zone that needs

the coldest water. This reduces the COP of the chiller in serving other zones. Also,

central plants require pump energy. Hydronic systems provide advantages such as

compact equipment and quiet operation. If central energy plants are used, the capable

engineer will seek to minimize the tendency of individual zone requirements to

degrade the efficiency of the central plant.

5.6 Economics of Optimized-Function HVAC

The idealized performance of optimized-function HVAC extends to its economics.

Human productivity is the highest cost associated with HVAC. By definition,



optimized-function HVAC provides the best comfort and health, so it offers the

greatest productivity. The second-highest cost of HVAC is energy. Life-cycle cost is

greatly reduced because optimized systems operate with the least possible energy.

Optimized HVAC reduces the cost of equipment space and increases rentable space.

Air handling rooms are eliminated. Duct space is minimized or eliminated.

5.7 Onward to the Future

Important changes in engineering often occur as seismic shifts, in which current

practices are abruptly abandoned and nascent approaches quickly rise to dominance.

Such upsets occur after years of increasing tension, when important realities grow too

strong to ignore. We are now at such a point in the design of HVAC systems. A

revolution in HVAC is needed to make buildings survivable in a century of very high

energy costs and terrorist threats.

The coming jolt in HVAC design is analogous to the extinction of the dinosaurs,

which grew too large and unadoptable and were replaced by small, versatile

mammals. Similarly, multiple zone air handling will be replaced by a versatile new

design concept that we have called optimized-function HVAC. The change begins

now. Design your HVAC systems for this century, not the last one.

CHAPTER SIX

Conclusion

Chapter 6 Conclusion


6.1 Conclusion

The proper design of HVAC system is one of the most fundamental factors for the

pharmaceutical industries. Systems have been designed for greatest assurance of

consistent environmental conditions, with constant volume or reheat and high air

change rates the order of the day. Steps to prevent cross-contamination in multi-

product plants have been draconian, ranging from 100% fresh air or exhaust to

multiple series HEPA filters in supply and exhaust. Developments in processing

equipment, isolation technology and a risk or science-based approach to ensuring

parameters of "strength, identity, safety, purity, and quality," open a new world of

possibilities for HVAC in pharmaceutical facilities.

The engineers are trying to modernization the HVAC design. Now more than

ever, regulators and quality professionals are open to the idea of managing the risks

inherent in environmental control rather than attempting to eliminate them and

creating new ones in the process. This requires a cross-functional approach, engaging

the departments of quality, devel

modern approach to hvac design and its future trend

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air system singleduct

control systems

fresh air

makeup air

recirculated air

multizone system dual

zone zoning design

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