Thermal and Fluids
in Architectural Engineering
8. Refrigeration and heat pump
Jun-Seok Park, Dr. Eng., Prof.
Dept. of Architectural Engineering Hanyang Univ.
Where do we learn in this chaper
1. Introduction 2.The first law
3.Thermal resistances
4. Fundamentals of fluid mechanics
5. Thermodynamics 6. Application
7.Second law 8. Refrigeration,
heat pump, and power cycle
9. Internal flow 10. External flow
11. Conduction 12. Convection 14. Radiation
13. Heat Exchangers 15. Ideal Gas Mixtures
and Combustion
8.1 Introduction
8.2 Vapor-compression refrigeration cycle 8.3 Heat pump
8. Refrigeration, heat pump, and
power cycle
8.1 Introduction
□ We use refrigeration and heat pump cycle for conditioning the buildings in every day life.
□ Renewable energy is also used combined with heat pump.
- Examples: GHP system
Entropy
M) W
- Q
(ΔE
8.1 Introduction
Entropy
M) W
- Q
(ΔE
Source : KOTEC자료
8.2 Vapor-compression refrigeration Cycles
□ Refrigerator or Air conditioners are devices that do move heat from law (Cold) to high (hot) spaces.
□ There are several types of refrigeration cycles
□ Vapor-compression refrigeration cycle is commonly used in a wide range of application
- Example) Refrigerator in HVAC, Air-conditioner
Entropy
M) W
- Q
(ΔE
8.2 Vapor-compression refrigeration Cycles
□ In practical problems,
- No device is to compress two-phase mixture
- A saturated liquid is expanded isentropically to a two phase mixture
□ Because of these practical considerations, the Carnot cycle is modified in two way,
- two-phase mixture is moved to a saturated vapor before the compressor
- A saturated liquid is expanded through irreversible throttling valve.
Entropy
M) W
- Q
(ΔE
8.2 Vapor-compression refrigeration Cycles
□ The working fluid in a vapor-compression refrigeration cycle is called as refrigerant.
- Example ) R-12, R-134a, ammonia, carbon dioxide.
□ The performance of a refrigeration cycle is evaluated through two quantities
- COP or “Tons of refrigeration”
Entropy
M) W
- Q
(ΔE
8.2 Vapor-compression refrigeration Cycles
□ COP (Coefficient of Performance)
□ Typical values of COP are from 1.5 to 5.0
Entropy
M) W
- Q
(ΔE
process) c
isenthalpi ) (
(
) (
W
) (
Q
; ) (
Q
) (
W W
Q Q
Q W
4 3 1
2 4 1 in
Ref
4 1 L
3 2 H
1 2 in
L H
L in
Ref
h h h
h h h COP Q
h h m h
h m
h h m COP Q
L L
8.2 Vapor-compression refrigeration Cycles
□ Tons of Refrigeration
- is measured early in the use of mechanical refrigeration - means that the heat transfer rate required to freeze 1 ton of
0 ℃ water into ice at 0 ℃ in 24 hours 1 TON of Refrigeration is 211kJ/min
Entropy
M) W
- Q
(ΔE
8.3 Heat pumps
□ Heat pumps are devices that use QH,
□ Typical values ranges from 3.0 to 6.0
□ Heat pumps are more expensive and complex than traditional gas, oil-fired heaters or electric resistance heaters
Entropy
M) W
- Q
(ΔE
1
) (
) (
Q Q
Q W
Q
Ref HP
1 2
3 2
L H
H
in H HP
COP COP
h h
h COP h
8.3 Heat pumps
□ But, COP is always greater than traditional system, and environment load is lower
□ because the COP and heating capacity decrease as the source temperature becomes low, a back up source of heat is often required.
- Examples) ground source, water source, river etc.
Entropy
M) W
- Q
(ΔE
