Will the COP of a refrigeration unit likely be larger when it chills room-temperature air to 3°C (as in your kitchen’s refrigerator) or when it chills room-temperature air to -18°C (as in your kitchen’s freezer)

The operating condition for the single compressor in a household refrigerator is the lowest box temperature, which is typically A. 0F B. -20F C. 20F D. 40F

Welded ______sealed compressors are normally used in household refrigerators.

Refrigeration

REFRIGERATION ENGINEERING (!) USE SHAPIRO AND MORAN TABLE

SUBJECT: THERMODYNAMIC COURSE: II ASSI.LACTURE: NATIQ ABBAS Example 2:- Refrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 MPa and -10°C at a rate of 0.05 kg/s and leaves at 0.8 MPa and 50°C. The refrigerant is cooled in the condenser to 26°C and 0.72 MPa and is throttled to 0.15 MPa. Disregarding any heat trans fer and pressure drops in the connecting lines between the components; determine (a) the rate of heat removal from the refrigerated space and the power input to the compressor, and (b) the coefficient of performance of the refrigerator. Solution: - P 0.14 MPa T=-10 C 212 h 246.36 kJ/kg da OF SAMARRA P 0.8 MPa VER h2 = 286.69 kJ/kg O P 0.72 MPa T= 26 C hg = 87.83 kJ/kg h3 =h = 87.83 KJ/kg h4 = h3 (throttling) h4 87.83 kJ/kg 0.8 MPa 50°C 0.72 MPa/ 26 C 0.15 MPa 0.14 MPa -10°C SUBIECT: THERMODYNAMIC COURSE: II ASSI.LACTURE: NATIQ ABBAS RING

SUBJECT: THERMODYNAMIC COURSE: II ASSI.LACTURE: NATIQ ABBAS Example 2:- Refrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 MPa and -10°C at a rate of 0.05 kg/s and leaves at 0.8 MPa and 50°C. The refrigerant is cooled in the condenser to 26°C and 0.72 MPa and is throttled to 0.15 MPa. Disregarding any heat trans fer and pressure drops in the connecting lines between the components; determine (a) the rate of heat removal from the refrigerated space and the power input to the compressor, and (b) the coefficient of performance of the refrigerator. Solution: - P 0.14 MPa T=-10 C dut 246.36 kJ/kg OF P 0.8 MPa h2 = 286.69 kJ/kg P 0.72 MPa T= 26 C h3 = 87.83 kJ/kg h3 = h = 87.83 KJ/kg h4 = h3 (throttling) h4 87.83 kJ/kg 0.8 MPa 0.72 MPa/ 26 C 0.15 MPa 0.14 MPa -10°C SUBJECT: THERMODYNAMIC COURSE: II ASSI.LACTURE: NATIQ ABBAS SAMARRA RING

5. A refrigerator with tetrafluoroethane as refrigerant operates with an evaporation temperature of 247.15 K (-26°C) and a condensation temperature of 300.15 K (27°C). Saturated liquid refrigerant from the condenser flows through an expansion valve into the evaporator, from which it emerges as saturated vapor. (a) For a cooling rate of 5.275 kW, what is the circulation rate of the refrigerant? (b) By how much would the circulation rate be reduced if the throttle valve were replaced by a turbine in which the refrigerant expands isentropically? (c) Suppose the cycle of (a) is modified by the inclusion of a countercurrent heat exchanger between the condenser and the throttle valve in which heat is transferred to vapor returning from the evaporator. If liquid from the condenser enters the exchanger at 300.15 K (27°C) and if vapor from the evaporator enters the exchanger at 247.15 K (-26°C) and leaves at 294.15 K (21°C), what is the circulation rate of the refrigerant?

3.) When a gas surrounded by air is compressed or expands adiabatically, its temperature rises or decreased even though there is no heat input or dissipated to the gas. Where does the energy come from to raise or lower the temperature? 4.) Why must a room air conditioner be placed in a window rather than just set on the floor and plugged in? Why can a refrigerator be set on the floor and plugged in?

please provide full calculations thank you