Refrigerant- 134 a enters the condenser of a residential...

Refrigerant- 134 a enters the condenser of a residential heat pump at $800 \mathrm{kPa}$ and $50^{\circ} \mathrm{C}$ at a rate of $0.022 \mathrm{kg} / \mathrm{s}$ and leaves at $750 \mathrm{kPa}$ subcooled by $3^{\circ} \mathrm{C}$. The refrigerant enters the compressor at $200 \mathrm{kPa}$ superheated by $4^{\circ} \mathrm{C}$. Determine (a) the isentropic efficiency of the compressor, ( $b$ ) the rate of heat supplied to the heated room, and ( $c$ ) the COP of the heat pump. Also, determine $(d)$ the $\mathrm{COP}$ and the rate of heat supplied to the heated room if this heat pump operated on the ideal vapor-compression cycle between the pressure limits of 200 and 800 kPa.

Refrigerant- 134 a enters the condenser of a residential heat pump at $800 \mathrm{kPa}$ and $50^{\circ} \mathrm{C}$ at a rate of $0.022 \mathrm{kg} / \mathrm{s}$ and leaves at $750 \mathrm{kPa}$ subcooled by $3^{\circ} \mathrm{C}$. The refrigerant enters the compressor at $200 \mathrm{kPa}$ superheated by $4^{\circ} \mathrm{C}$. Determine
(a) the isentropic efficiency of the compressor, ( $b$ ) the rate of heat supplied to the heated room, and ( $c$ ) the COP of the heat pump. Also, determine $(d)$ the $\mathrm{COP}$ and the rate of heat supplied to the heated room if this heat pump operated on the ideal vapor-compression cycle between the pressure limits of 200 and 800 kPa.

Key Concepts

Vapor-Compression Cycle

This cycle is the fundamental process used in refrigeration and heat pump systems. It involves the compression of a refrigerant gas, its condensation to a liquid at a high pressure, expansion to a lower pressure, and subsequent evaporation to absorb heat. Understanding this cycle is key to analyzing system performance, assessing energy flows, and calculating quantities like the rate of heat transfer and system efficiency.

Refrigeration Heat Pump

A refrigeration heat pump is a system that transfers heat from a cooler space to a warmer space by using external work, typically through a compressor. In this context, it is designed to deliver heat to a heated room, and its performance is measured by how effectively it can convert input work into heat output, which is evaluated via parameters such as the coefficient of performance (COP).

Isentropic Efficiency

Isentropic efficiency quantifies the performance of a compressor by comparing the actual work input to the ideal work input required for an isentropic (reversible and adiabatic) process. A high isentropic efficiency indicates that the compressor is performing close to its ideal behavior, which is crucial for accurately determining the work required and the overall efficiency of the thermodynamic cycle.

Coefficient of Performance (COP)

The coefficient of performance (COP) is a measure of the efficiency of a heat pump or refrigeration system. It is defined as the ratio of useful heating or cooling provided to the work input. A higher COP indicates a more efficient system, and calculating the COP involves understanding the energy exchanges during compression, condensation, expansion, and evaporation processes in the cycle.

Superheating and Subcooling

Superheating and subcooling refer to the controlled adjustments of the refrigerant's temperature relative to its saturation temperature. Superheating occurs when the vapor is heated above its saturation temperature, which can ensure that the refrigerant remains in a vapor state before entering the compressor. Subcooling occurs when the liquid refrigerant is cooled below its saturation temperature, which prevents vaporization before the expansion process. Both processes are important in managing the quality of the refrigerant and optimizing the performance of the cycle.

Thermodynamic Properties of Refrigerants

Understanding the thermodynamic properties of refrigerants, such as pressure, temperature, enthalpy, and entropy, is essential for analyzing the performance of refrigeration and heat pump systems. These properties allow engineers to determine state points, evaluate phase changes, and perform energy and mass balance calculations within the vapor-compression cycle, ultimately influencing parameters like work, heat transfer, and efficiency.

Transcript

00:01 Hello friends here it is given heat pump cycle in which refrigerant is r134a.

00:33 We have to find isometric efficiency of compression rate of heat supply to the heated room coefficient of performance of pump and coefficient of performance of pump for heat for heated room if heat pump to be operated on ideal vapor compression cycle between the same pressure limit are to be determined so given heat pump operated on ideal vapor compression between same pressure limit let us here is the analysis we have to use fluid property of r134a using table a11 to a13.

03:20 Let us see here.

03:21 At state 2 pressure p2 is 800 kilo pascal and temperature is 50 degrees celsius that is for condensation.

03:37 Anthalfi is to 86 .71 kilojoule per kg temperature t3 is the saturated temperature temperature at the rate of 750 kilo -pascal to be 29 .06 degrees celsius.

04:10 At straight 3, p3 is 750 kilopascal and temperature t3 is 29 .06 minus 3, that is 26 .06 degrees celsius.

04:31 And entropy is, sorry, enthalpy is 87.

04:37 93 kilojoule per k .g.

04:47 In state 1 that is for pump pressure is 200 kilo pascal.

05:00 Temperature t1 is minus 10 .09 plus 4 that is minus 6 .09 degrees celsius.

05:15 Anthalfi is 247 .08 kilojoule per kg and entropy is 0 .95 .95.

05:26 07 kilojoule per kg per kelvin.

05:42 In state 2, pressure is 800 kioskal, entropy s2 is called to h1, an enthalpy of saturated fluid is 277 .28 kilojoules per k .g.

06:04 Iscentrophic efficiency of the compression entropy in state 2.

06:14 In eccentric process minus h1 upon h2 minus h1 putting the value 277 .28 minus 247 .88 divided by 286 .71 minus 247 .81 minus 247 .88...

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