Thermal efficiency of refrigeration cycle

The coefficient of performance is used to quantify the performance of refrigeration cycles. Refrigeration is the achievement of temperatures below that of the local environment.

Therefore the waste heat can be utilized by the thermoelectric device to generate electrical power which can be used as a supplement to the compressor of the refrigeration cycle.

Thermal efficiency of refrigeration cycle. The thermal efficiency of the cycle can be calculated as q evap w comp h 1 h 4 h 2s h 1 Common Refrigerants There are several fluorocarbon refrigerants that have been developed for use in VCRC. R11 R12 CCl 2F 2 dichlorodifluoromethane - used for refrigeration systems at higher temperature levels - typically water chillers and air conditioning R22 CHClF. For a refrigeration or heat pumps thermal efficiency indicates the extent to which the energy added by work is converted to net heat output.

From an economic point of view the best refrigeration cycle is one that removes the greatest amount of heat from the inside of the refrigerator cold reservoir for the least expenditure of mechanical work or electric energy. The main purpose of this paper is to evaluate the efficiency of a power system that comprises a Rankine cycle linked to a refrigeration cycle. More specifically the objectives are.

I to develop mathematical and numerical models for various thermodynamic systems. Ii to optimize these systems. And iii to identify the systems that can provide a higher efficiency than that of the basic Rankine cycle.

The refrigerating capacityQ o and the required powerPare calculated from the mass ow of the refrigerant mR Q o m R qo. PNU m R wrevtNU. 8 The specic work for the reversible processwrev tNU and the specic refrigerating heatqo of the CARNOT cycle are shown in gure 3 as areas in a temperature-entropy-diagram.

The coefcientCOPNUC depends only on the tempera-. The coefficient of performance is used to quantify the performance of refrigeration cycles. The symbol used for coefficient of performance is COP with a subscript R for refrigeration.

Just like the efficiency of power cycles the COP is defined as the ratio of the desired output to the required input. Diagram the ratio of the area enclosed by the cyclic curve to the area under the heat-addition process curve represents the thermal efficiency of the cycle. Any modification that increases the ratio of these two areas will also increase the thermal efficiency of the cycle.

The thermal efficiency in terms of the compressor pressure ratio PR p 2 p 1 which is the parameter commonly used. In general increasing the pressure ratio is the most direct way to increase the overall thermal efficiency of a Brayton cycle because the cycle approaches the Carnot cycle. The efficiency of a refrigerator is called the coefficient of performance K is given by.

K Q c Q h Q c Q c W d o n e 1 ϵ ϵ where Q c is the heat absorbed while Q h is the heat releasedlost w d o n e is the work done on the engine and e. The efficiency of the Stirling cycle is the same as that of the Carnot cycle. Thats why the cycle is reversible and all reversible cycles have the same efficiency.

If the efficiency of the regenerator is nr then heat taken in from the regenerator during. Refrigerant-134a is the working fluid in an ideal compression refrigeration cycle. The refrigerant leaves the evaporator at -20oC and has a condenser pressure of 09 MPa.

The mass flow rate is 3 kgmin. Find COPR and COPR Carnot for the same Tmax and Tmin and the tons of refrigeration. Using the Refrigerant-134a Tables we have State Compressor inlet TC x h.

For a refrigeration or heat pumps thermal efficiency indicates the extent to which the energy added by work is converted to net heat output. From an economic point of view the best refrigeration cycle is one that removes the greatest amount of heat from the inside of the refrigerator cold reservoir for the least expenditure of mechanical work or electric energy. The coefficient of performance of a refrigeration cycle may be increased by using thermoelectric generator in a proper arrangement.

Therefore the waste heat can be utilized by the thermoelectric device to generate electrical power which can be used as a supplement to the compressor of the refrigeration cycle. Hence new thermal efficiency after solving equation 1 η 1 T 3 T 1 Which is equal to Carnot Cycle efficiency. Thermal efficiency is a measure of the performance of a power cycle or heat engine.

The symbol for thermal efficiency is the Greek letter ETA η. It is a lower case h in the Symbol font if you ever need to type it. The thermal efficiency is defined as the ratio of the desire output of the cycle to the required input for the cycle.

The goal of the power cycle is to produce a net amount of work W HE so this goes in. The Carnot Cycle is an entirely theoretical thermodynamic cycle utilising reversible processes. The thermal efficiency of the cycle and in general of any reversible cycle represents the highest possible thermal efficiency this statement is also known as Carnots theorem - for a more detailed discussion see also Second Law of Thermodynamics.

Refrigeration is the achievement of temperatures below that of the local environment. The main purpose of refrigeration is thermal conditioning eg. For food preservation or air conditioning and the basic apparatus is a refrigerator a thermal machine producing cold.

Other names for special types of. Compression refrigeration cycles in general take advantage of the idea that highly compressed fluids at one temperature will tend to get colder when they are allowed to expand. If the pressure change is high enough then the compressed gas will be hotter than our source of cooling outside air for instance and the expanded gas will be cooler than our desired cold temperature.