design lecture notes chp 1
DESCRIPTION
design lecture notesTRANSCRIPT
-
FOOD ENGINEERING DESIGN AND ECONOMICS
CHAPTER I
ENGINEERING DESIGN
-
Engineering Design
Engineering design is planning a system a part of a system or a process in the way which corresponds the needs. Design is a job of making decisions. Where the data at hand are integrated with basic sciences, mathematics and engineering knowledge in the most suitable manner and the target is achieved. -
Stages of Design
Determination of the aim(s) and desired criteria (need)
Collection of data and bring up them together (synthesis)
Detailed investigation of the subject (analysis)
Regulation and starting the application (construction)
Trials (testing)
Examination of the results (evaluation)
- Engineering design is an imaginary jump from the realities of today to the probabilities of future.Engineering design is a creative activity; it supplies the formation of new and helpful things that was not present before.Engineering design is the conversion of data in the form of needs to data in the form of technical systems by the help of human and technical power.Engineering design is a problem solving activity directed to a target.
-
A sample model for Engineering Design
Step 1. Recognizing the need.Step 2. Defining the problem.Step 3. Planning the project.Step 4. Gathering information.Step 5. Conceptualizing alternative approaches.Step 6. Evaluating the alternatives.Step 7. Selecting the best alternative.Step 8. Communicating the design.Step 9. Implementing the preferred design. -
Process Design Development
Types of Design
Preliminary or quick estimate designs
Detailed estimate designs
Firm process or detailed designs.
-
i. Preliminary or quick estimate designs
Preliminary designs are ordinarily used as a basis for determining whether further work should be done on the proposed process. The design is based on approximate process methods and rough cost estimates are prepared. Few details are included and the time spent on calculations is kept at a minimum. -
ii. Detailed estimate designs
If the results of the preliminary design show that further work is justified, a detailed estimate design may be developed. In this type of design, the cost and benefit potential of an established process is determined by detailed analysis and calculations. However, exact specifications are not given for the equipment and drafting work is minimized. -
iii. Firm process designs or detailed designs
When the detailed estimate design indicates that the proposed project should be a commercial success, the final step before developing construction plans for the plant is he preparation of a firm process design. Complete specifications are presented for all components of the plant and accurate costs based on quoted prices are obtained. The firm process design includes blue prints and sufficient information to permit immediate development of the final plans for constructing the plant. -
Feasibility survey
In a feasibility survey process involved must be considered along with the existing and potential market conditions for the particular product. A preliminary feasibility survey gives an indication of the probable success of the project and also shows what additional information is necessary to make a complete evaluation.(A need does not mean that, it is;reasonable
desirable
possible to fulfill that need)
- Following is a list of items that should be considered in
making a feasibility survey:
Raw materials (availability, quantity, quality, cost)
Chemical an physical processes (equilibrium, yields, rates, optimum conditions)
Facilities and equipment available at present
Facilities and equipment which must be purchased
Estimation of production costs and total investment
Profits (probable and optimum, based per mass of product and per year or return on investment)
Materials of construction
Safety considerations
-
Markets (present and future supply and demand, price changes, location and number of possible customers)
Competition (overall production statistics, comparison of manufacturing processes, product specifications of competitors)
Properties of products
Sales and sale service (distribution, advertisement, technical services)
Shipping restrictions and containers
Plant location
Patent situation and legal restrictions
-
+ time of the project
-
Process development
In many cases, the preliminary feasibility survey indicates that additional research, laboratory or pilot plant data are necessary and a program to obtain this information may be initiated. Process development on a pilot-plant or semi-work scale is usually desirable in order to obtain accurate design data. - By process development the following information are obtained:
material and energy balances
process conditions
yields
rates
grades of raw materials and products
batch versus continuous operation
materials of construction
operating characteristics
and other design variables.
-
Preliminary (or quick estimate) designs
The primary step in preparing the preliminary design is to establish the bases for design. The basic items are;the properties of the product and the manufacturing process
availability and quality of raw material
annual operating factor
energy requirements
valuable by-products
- The next step consists of preparing a simplified flow diagram
showing details of the process. Flow rates and stream conditions
for the remaining cases are evaluated by:
material balances
energy balances
raw material-product relationships and properties
yields
- The final stage of preliminary design is writing a report which will present the results of the design work. This report shows calculations and design details therefore improves communication.As soon as sufficient data are available from feasibility survey or process development the preliminary design should be carried out so that money and time losses for undesirable projects are eliminated.
- Before detailed estimate design;
manufacturing process
material and energy balances
temperature and pressure ranges
raw material and product specifications
yields, reaction rates, time cycles, capacity
materials of construction
utility requirements
plant site
are to be established.
-
Detailed estimate designs
The preliminary design leads the accurate estimation ofrequired capital investment
manufacturing costs
potential profits
Based on these the following factors should be determined in detailed estimate design stage.
types of buildings, heating, ventilating, lighting, power supply, drainage, waste disposal, safety facilities and instrumentation.
-
Firm process design or Detailed design
At this stage all detailed drawings are prepared and real investments are determined.A complete plant layout (production lines, facilities etc), blueprints and instructions for construction are developed.Specifications are given for warehouses, laboratories, guard-houses, fencing, change houses, transportation facilities etc.MUST BE DEVELOPED WITH THE ASSISTANCE OF PERSONS SKILLED IN VARIOUS ENGINEERING FIELDS. -
Construction and Operation
When a definite decision to proceed with the construction of a plant is made, there is usually immediate demand for a quick plant start-up. (why?)The design engineer should work closely with construction personnel during the final stages of construction and purchasing.During construction of the plant, the design engineer should visit the plant site to assist in interpretation of the plans and learn methods for improving future designs. - The engineer should also be available during the initial start up of the plant and the early phases of operation. Thus, by close team work between design, construction and operational personnel, the final plant can develop from the drawing board stage to an operating unit that can function both efficiently and effectively.
-
Comparison of Different Processes
Technical factors
Process flexibility
Continuous operation
Special controls involved
Commercial yields
Technical difficulties involved
Energy requirements
Special auxiliaries required
Possibility of future developments
Health and safety hazards involved.
-
Raw Materials
Present and future availability
Processing required
Storage requirements
Materials handling problems.
Waste products and by-products
Amount produced
Value
Potential markets and uses
Manner of discard
Environmental aspects
-
Equipment
Availability
Materials of construction
Initial costs
Maintenance and installation costs
Replacement requirements
Special designs
For specification: identification, function, operation (continuous or batch), materials handled (quantity, composition, physical properties), basic design data, essential controls, insulation (temperature, air, noise), requirements, allowable tolerances, special information and details are to be given.
-
Plant location
Amount of land required
Transportation facilities
Nearness to markets and raw material sources
Availability of services and power facilities
Availability of labor
Climate
Legal restrictions and taxes
-
Costs
Raw materials
Energy
Depreciation
Other fixed charges
Processing and overhead
Special labor requirements
Real estate
Patent rights
Environmental controls.
-
Time factor
Project completion deadline
Process development required
Occurrence at right time from market standpoint
Value of money.
Process considerations
Technological availability
Raw materials common with other processes
Consistency of product within company
General company objectives.