Vapour compression cycle ENERGY MANAGEMENT HANDBOOK Sixth Edition

Vapour compression cycle (“ ENERGY MANAGEMENT HANDBOOK” Sixth Edition, Chapter 8) • Refrigerator • Air conditioning plant • Heat pump 1

Refrigerator 2

Electric-motor-driven vapour compression cycle 3

Engine-driven vapour compression cycle 4

Absorption heat pump 5

Applications of Heat pumps • • space heating; heating and cooling of process streams; water heating for washing, sanitation and cleaning; steam production; drying/dehumidification; evaporation; distillation; concentration. 6

Heat pump performance Heat source at 0 C 7

Typical COP 8

Heat Transformer Pressure Temperature 9

Factors affecting heat pump performance • the climate - annual heating and cooling demand maximum peak loads; • the temperatures of the heat source and heat distribution system; • the auxiliary energy consumption (pumps, fans, supplementary heat for bivalent system etc. ); • the technical standard of the heat pump; • the sizing of the heat pump in relation to the heat demand the operating characteristics of the heat pump; • the heat pump control system. 10

How heat pumps achieve energy savings and CO 2 emissions reduction • Heat pumps and energy saving • An efficient technology • A large and worldwide potential 11

Heat sources Heat source Temperature Range (°C) Ambient air -10 +15 Exhaust air +15 +25 Ground water +4 +10 Lake water 0 +10 Rock 0 +5 Ground 0 +10 Waste water >10 12

Heat pump working fluids • HFC-134 a • R-407 C • Natural working fluids 13

Heat pumps in residential and commercial buildings 14

Example of how the COP of a water-to-water heat pump varies with the distribution/return temperature. 15

Fundamental physics for vapor compression cycles 16

Constant-pressure change from liquid to vapour phase for a pure substance. 17

Temperature change of substance at constant pressure and constant heat supply 18

Temperature-volume diagram showing liquid and vapour phases for different constant pressures 19

Temperature-volume diagram showing liquid and vapour phases 20

Ideal vapour compression cycle 21

Relations for the cycle 22

Ideal cycle 3 4 2 1 23

Log P vs Enthalpy diagram Constant Entropi Absolute Pressure Saturated liquid Constant Temperature Saturation area Saturated vapour Enthalpy 24

Coefficient of performance • The coefficient of performance of a refrigeration system is • The coefficient of performance of a heat pump system is 25

Efficiency of compressor 26

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Sweden - Closed-cycle compression heat pump 28

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Example refrigerator/Heat Pump • An refrigerator has an cooling capacity of 500 W. Evaporator pressure 2 bar(a), Condenser pressure 10 bar(a). An ideal cycle is assumed Determine • Power input to compressor • Heat transfer rate from Condenser 30

Solution 31