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Vapour compression cycle. Refrigerator Air conditioning plant Heat pump. ( “ ENERGY MANAGEMENT HANDBOOK” Sixth Edition, Chapter 8). Refrigerator. Electric-motor-driven vapour compression cycle. Engine-driven vapour compression cycle. Absorption heat pump. Applications of Heat pumps.
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Vapour compression cycle • Refrigerator • Air conditioning plant • Heat pump (“ ENERGY MANAGEMENT HANDBOOK” Sixth Edition, Chapter 8)
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.
Heat pump performance Heat source at 0 C
Heat Transformer Pressure Temperature
Factors affecting heat pump performance • the climate - annual heating and cooling demand and 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 and the operating characteristics of the heat pump; • the heat pump control system.
How heat pumps achieve energy savings and CO2 emissions reduction • Heat pumps and energy saving • An efficient technology • Alarge and worldwide potential
Heat pump working fluids • HFC-134a • R-407C • Natural working fluids
Example of how the COP of a water-to-water heat pump varies with the distribution/return temperature.
Constant-pressure change from liquid to vapour phase for a pure substance.
Temperature change of substance at constant pressure and constant heat supply
Temperature-volume diagram showing liquid and vapour phases for different constant pressures
Ideal cycle 3 2 4 1
Log P vs Enthalpy diagram Constant Entropi Absolute Pressure Saturated liquid Constant Temperature Saturation area Saturated vapour Enthalpy
Coefficient of performance • The coefficient of performance of a refrigeration system is • The coefficient of performance of a heat pump system is
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