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Unformatted text preview: determine the required power input (in kW). ME 201 Thermodynamics Spring 2006 2 Solution: We begin by drawing the interaction diagram for this refrigerator High Temperature Heat Reservoir (kitchen) at T H Low Temperature Heat Reservoir (freezer) at T L Refrigerator Q H Q L W net By definition we have for our refrigerator COP = Q W L net If we can determine the required heat transfer for freezing the chickens, Q chick , then we can use Q L = -Q chick and solve for W net , In the freezing process for the chicken, we have three processes: Lowering the chicken temperature from 15 ° C to its freezing point Q 1 = mc(T 2-T 1 ) = (35)(3.32)[(-2.8)-15] = -2068.4 kJ Freezing the chicken Q 2 = m(-latent heat of fusion) = (35)(-247) = -8645 Lowering the chicken temperature from its freezing point to -20 ° C Q 3 = mc(T 3-T 2 ) = (35)(1.77)[-20-(-2.8)] = -1065.5 kJ Then Q L = -Q chick = -(Q 1 +Q 2 +Q 3 ) = 11,779 kJ ME 201 Thermodynamics Spring 2006 3 and W = Q COP = 11,779 4.3 = 2739 kJ net L The power required is & W = W t = 2739 (3)(3600) = 0.25 kW net net Δ...
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This note was uploaded on 07/25/2008 for the course ME 201 taught by Professor Somerton during the Spring '06 term at Michigan State University.
- Spring '06