Air_Conditioner - MAE - EML 4304C Thermal/Fluid Design and...

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Unformatted text preview: MAE - EML 4304C Thermal/Fluid Design and Lab Lab 5 Refrigeration Experiment MAE - EML 4304C Thermal/Fluid Design and Lab Lab Objective Determine the performance of an air-conditioning system. Measure temperature and pressure at four critical points. Measure the mass flow rate of the working fluid. Measure power required by the fans and the compressor. To accomplish objective: MAE - EML 4304C Thermal/Fluid Design and Lab Refrigerator Terms The transfer of heat from lower temperature regions to higher temperature ones is called refrigeration . Devices that produce refrigeration are called refrigerators. The cycles on which they operate are called refrigeration cycles. The working fluids used in refrigerators are called refrigerants. Vapor compression used for the purpose of heating a higher temperature space by transferring heat from a cooler medium are called heat pump . MAE - EML 4304C Thermal/Fluid Design and Lab Refrigeration Refrigeration may be achieved by: vapor compression systems expansion of compressed gases absorption cycle thermal-electric effects. Refrigeration is the transfer of energy in the form of heat from a colder body to a hotter body, by the application of external work. It works like a reversed heat engine. MAE - EML 4304C Thermal/Fluid Design and Lab Coefficient of Performance (COP) The useful effect of the refrigerator is the removal of heat from the cold space i.e. what we get is Q 1 and we have to put in work W from a compressor. Thus, Conversely, the useful effect of the heat pump is the addition of heat to a hot space i.e. we get Q 2 for putting in work input W . Thus, 0 < COP refrig < the larger, the better. 1 < COP heat pump < the larger, the better. Desired effect MAE - EML 4304C Thermal/Fluid Design and Lab Three refrigeration cycles a b Reversed Carnot cycle Ideal cycle Actual cycle Compressor h1 h2 Wc Q = ? Wc = h2-h1, Both pressure and temperature increase during this compressing process MAE - EML 4304C Thermal/Fluid Design and Lab Carnot Refrigeration Cycle This simple cycle is impractical because of the following reasons: There are always finite temperature differences in condenser and evaporator for heat transfer from or to the working fluid (thus not reversible). Process 1 2 involves the compression of a mixture of liquid and vapor until all the liquid has evaporated. This is very difficult to achieve in practice, because the compression of wet mixtures is very difficult to implement mechanically. a b MAE - EML 4304C Thermal/Fluid Design and Lab Carnot Refrigeration Cycle 1 2 isentropic (reversible adiabatic) compression 2 3 isothermal heat rejection (condensation) 3 4 isentropic (reversible adiabatic) expansion 4 1 isothermal heat absorption (evaporation) ( 29 ( 29 c h c b a c h b a c...
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This note was uploaded on 02/14/2012 for the course EML 4034c taught by Professor Abbitt during the Spring '12 term at University of Florida.

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Air_Conditioner - MAE - EML 4304C Thermal/Fluid Design and...

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