sahpa ® south african heat pipe association energy postgraduate conference epc2013, 11-14 aug 2013...
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SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 3 Pre-amble (cont.)TRANSCRIPT
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
DH Jeggels and RT Dobson
Department of Mechanical Engineering,University of Stellenbosch,
Stellenbosch, Western Cape Province, South AfricaDawood Jeggels and RT Dobson presentation for EPC2013 as at 8 August 2013
Theoretical and Experimental Simulation
of a
Li-Br Water Dual Function Absorption system
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
2
Preamble
The world, in general, has become very aware of the fact that we are polluting the planet irreversibly; “you don’t get nothing for free” so if “If it isn’t green, paint it green”.
Environmental impact studies, global warming, ozone depletion, pollution, renewable energy such as solar, “CSP”, wind, tidal, hydroelectric and waste minimization have all become important words in both business and academic circles.
Power utilities and big-business must be seen to be saving energy, generating power more efficiently, reducing their carbon footprint, and reducing their production of polluting and global warming effluent/waste/toxic materials.
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
3
Power stations using a Rankine cycle or a Brayton cycle reject some 33% of the energy supplied, “irreversibly”, back into the environment.
The higher the source temperature the higher the thermal efficiency
The lower the waste temperature the higher the thermal efficiency BUT the rate of improvement decreases and the power generating equipment becomes exponentially more expensive
The idea is then to combine a Rankine cycle which is more efficient at higher temperature with another cycle which is more efficient at a lower temperature and thereby increase the overall efficiency
Pre-amble (cont.)
=1− 𝑇 sink +273𝑇 source +273
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
4
Pre-amble (cont.)
Thermal efficiency as a function of heat source temperature
14% of 100°C waste heat can be recovered using a DFAC
Stirling cycle engine (SC)
Rankine cycle (RC)
Dual function absorption cycle (DFAC)
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
5
Contents
Preamble
Why a dual function absorption cycle
Objectives: To build and test an absorption system that can be used to get a better understanding of its functioning and control
strategies and to assist in validating the theoretical simulation model of the cycle
Experimental Apparatus
Transient theoretical modelling
Discussion, Conclusions and Recommendations
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
6
+ - ~
turbineW
Electrical generator
Turbine
Super heater
ionrefrigeratQ
Evaporator
Absorber
Pump
coolingQ
Waste heat supply
Control Valve
Rectifier
Vapour generator
hwm
12°C
hwT
refrigm refrigT
-8°C
58°C 58°C
82°C
Recouperator
58°C
58°C
280kPa
22°C, 44kPa
Figure 1 Dual function (power and refrigeration ammonia-water absorption system
74°C
27°C
Dual function (power and refrigeration) ammonia-water (or Li-Br water) absorption
system
Power
Refrigeration
Cooling water
Waste heat
supply
How does it work
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
7
�ሶେ�
�ሶେ� �ሶେେେ�� �ሶେେେ��
PGC TGC
Generator-Condenser vapour space
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Tamb
�ሶେ�
�ሶେ�� TGhw
TCcw
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�ሶ
PEA TEA mEA
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�ሶୡୟ୮
�ሶୡୟ୮
TE mE TEhw
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�ሶ �ሶ
Tamb
TA
THEAG
Tamb
�ሶ୪୭ୱୱ
mALF TALF
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THEGA
TAcw �ሶ
Figure 1 Schematic layout of the absorption cycle system
TCLP mCLP mG TG
�ሶ
CG
CALF
CA mA
mGC
Evaporator-Absorber vapour space
TcapE
Capillary tube dcap and Lcap
Generator
Absorber Evaporator
Pump
Condenser liquid pool
Heat Exchanger
Control valve
�ሶୡୟ୮
Control valve
TCLF
Experimental apparatus
Stand, generator
and condenser
Heat exchangers
Evaporator and
absorber
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
8
Theoretical Simulation Process
Figure Error! No text of specified style in document..1: Conservation equations control volumes, (a) Mass, (b) Momentum, (c) Energy
g
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z
(a) (b) (c)
Conservation of mass
Conservation of energy (Ignoring KE and PE )
and noting that h = u + PdV
Conservation of energy where Conservation of mass
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
9
Results
For example, for the Generator-Condenser, and similarly for the rest
2 164 326 488 650 812 974 1136129814601622178419462108227024320
10
20
30
40
50
60
70
80
90
Time, t (s)
Tem
pera
ture
, T (°
C) TG
TCl
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
10
Discussion, Conclusions and Recommendations
• We have shown what an absorption cycle works and how it can generate both power and cooling using a low-grade (low temperature) source of (waste) heat
• We have shown how we mathematically simulate such a system
• We have so far completed the generator-condenser/turbine part, the absorber-evaporator, the pump.
• We have manufactured the parts but still need to complete the assembly of the system parts
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
11
AcknowledgementsSouth African Heat Pipe Association
University of Stellenbosch
Thanks
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
12
Condenser
Stand
Generator
Back
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
13
Heat exchangers
Back
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SAHPA®
South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013
iThemba LABS
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Evaporator and absorber
Evaporator Absorber
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