Difference between heat engine heat pump and refrigerator pdf

The coefficient of performance or cop sometimes cp or cop of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work required. In a heat engine, heat is transferred from a higher temperature level called source to a lower temperature level called sink. This is accomplished by absorbing heat from a low temperature source, such as well water or cold outside air in winter, and supplying this heat to the hightemperature. Heat is transferred from the lower temperature level to higher temperature by applying external work to maintain the temperature below atmospheric temperature. This is done by extracting the heat from a cold body and delivering it to a hot body q 2. The principal difference between a heat pump and a refrigerator is a matter of perspective. The objective of a heat pump, however, is to maintain a heated space at a high temperature. In other words, a heat pump attempts to cool down the air outside the building, and in the process heats up the air inside the building. All irreversible refrigerators or heat pumps working between the.

Let us derive an expression for the efficiency of a heat engine. A refrigerator is a device that uses electric energy to transfer thermal energy from a cooler location to a warmer location. Similarly, a refrigerator moves heat from inside the cold icebox the heat source to the warmer roomtemperature air of the kitchen the heat sink. The coefficient of performance for a heat pump is the ratio of the energy delivered at the higher temperature to the work put into the system, cop q high q high q low. Winterbone freng, ba, bsc, phd, dsc, ali turan, in advanced thermodynamics for engineers second edition, 2015. A heat pump is a refrigerator whose inside is the great outdoors and whose outside is the room to be heated. Identify the main components of these 2 devices using a sketch. Examples of a heat engine is a refrigerator, heat pump, and carnot cycle. The carnot engine model was graphically expanded by benoit paul emile clapeyron in 1834 and mathematically explored by rudolf clausius in 1857 from which the concept of entropy emerged. What is the difference between heat pump and refrigerator.

The amount of heat which is transformed into mechanical energy is known as available energy of the cycle. Another device that transfers heat from a lowtemperature medium to a high temperature one is the heat pump. Thermodynamics definitions and terminology engineers edge. What is the difference between heat engine and heat pump. For refrigeration, the objective is to remove ql at tl, from the refrigerated. A hot body at fixed temperature t1 from which heat engine can draw heat sink. Also, for the heat pump, the efficiency increases when the temperature difference between the. Some external work is performed by the compressor of the refrigerator and then heat q 1 is rejected to the source, to the radiator of the refrigerator. Heat engines kelvin planck law refrigerators claussius statement entropy principle three statements of the second law heat engines a heat engine takes in heat at a high temperature and. The efficiency can be improved by maximising the difference between the hot inlet and cold exhaust temperatures of the working fluid during the heat cycle. Functionally, such engines are used in two ways, distinguishing a target reservoir and a resource or surrounding reservoir.

A carnot heat engine is a theoretical engine that operates on the carnot cycle. In heat engine the heat supplied to the engine is converted into. Thermal systems with small temperature differences between a hot side and a cold side also suffer from difficulties due to heat transfer pinch point effects. What is the difference between heat engine,heat pump. The production of work from heat requires a temperature gradient. Heat pump extracts heat q 1 from a cold body and delivers it to a hot body. A heat pump is a mechanical compression cycle that can be reversed to either heat or cool a controlled space. Heat is transferred from the lower temperature level to higher temperature by applying external work to maintain the. Understanding a refrigerator is a little harder than understanding a heat engine. Heat engine and efficiency a heat engine is a device by which a system is made to undergo a cyclic process that results in the conversion of heat to work. The only point of difference between the two is of the operating temperatures.

Demonstrate how a heat pump works to warm an interior space. What is the difference between carnot heat engine and a. Second, it means that heat pumps work best when temperature differences are small. Heat pumps and refrigerators heat engines can run in reverse send in energy energy is extracted from the cold reservoir energy is transferred to the hot reservoir this process means the heat engine is running as a heat pump a refrigerator is a common type of heat pump an air conditioner is another example of a heat pump. We will also look at how heat pumps can be more effective at heating our houses than an electric. Carnot states that the efficiency of the heat engine is independent of the type of fluid and only depends upon the maximum and minimum temperatures during the cycle. Refrigerator is a reversed heat engine which either cool or maintain the temperature of a body t 1 lower than the atmospheric temperature ta. Coefficient of performance an overview sciencedirect. The main purpose of the refrigerator is to chill or cool or freeze the substance, by maintaining very low temperature in the freezer. Calculate the coefficients of performance of the refrigerator and heat pump working with ammonia as the refrigerant. Figure 5 shows the heat pump seasonal coefficient of performance scop as a function cf the house heat pump thermal balance point. Which among the following is correct relation between cop of heat pump and cop of refrigerator. If q2 is the heat supplied to the engine and q1 is the heat rejected continued. Heat engine took q2 amount of heat from the hot body and did work equivalent to w e.

Pdf global efficiency of heat engines and heat pumps with non. Recognize some practical applications in real devices. This is the second lecture on refrigeration and air conditioning. It is equal to the difference between the heat received during the cycle from the hot. A heat mover transfers heat from one object to another. Explain what makes b c the carnot cycle the most efficient. Difference between a heat engine, refrigerator and heat pump. Heat engine, heat pump and refrigerator difference. A metric for devices of this type is the coefficient of performance, defined as. Heat engine efficiency depends between the maximum and minimum temperature of the cycle. Carnot refrigerator or carnot heat pump a refrigerator or heat pump that operates on the reversed carnot cycle. It is possible to describe a heat engine heat pump with 3 stages, but calculating the changes in thermodynamic properties, work, and heat in each. Refrigerators and heat pumps operate on the same cycle but differ in their objectives.

Many cycles can run in reverse to move heat from the cold side to the hot side, making the cold side cooler and the hot side hotter. Heat is always transferred from a hotter object to a colder object. Laboratory exercise 12 thermal efficiency heat engine a heat engine uses the temperature difference between a hot reservoir and a cold reservoir to do work. In this modules problems and exercises, you will show that cop ref cop hp. The basic model for this engine was developed by nicolas leonard sadi carnot in 1824. Thus, there is no difference between the cycle of operation of a heat pump and a refrigerator. The operating principle of the refrigeration cycle was described mathematically by sadi carnot in 1824 as a heat engine. Thus the efficiency of the heat engine is higher when operates on superheated steam. Difference between heat engine,refrigerator and heat pump. A refrigerator is designed to maintain a refrigerated space at a low temperature.

A heat pump transfers heat, to the hot reservoir as the target, from the resource or surrounding reservoir. The cycle and the heat and work transfers are indicated in figure 3. It should also be emphasized that there is a strong link between exergy and entropy since entropy production the term. Compare the heat pump and refrigerator in terms of their heat transfer, ql and qh, objectives p. As we know our household refrigerator maintains low temperature inside the freezer by absorbing the heat from this low temperature compartment and liberating it to atmosphere which is at high temperature. A refrigerator transfers heat from a cold region to a hot region. The efficiency of a heat pump is best when the temperature difference between the hot and cold reservoirs is least. When used as a heat engine, heat from the hot reservoir is used to do work by running a current through a load resistor. A heat pump is simply a refrigerator where the inside of the refrigerator is outside the house.

Mechanical engineering channel anuniverse 22 has started to stand on the shoulders of engineering giants and now, it is a place to hang out to learn the basics of mechanical engineering. It is an inefficient processmost of the energy is lost as waste heat. Heat engine, refrigerators and heat pumps self study point. The basic heat pump cycle is identical to the vaporcompression refrigeration cycle shown in figures 1 and 2, the only difference between a heat pump and a refrigerator being their basic functions. Feb 10, 2018 difference between refrigerator and heat pump 1 transfer of heat.

In ac the compressor and condenser are in separate unit from the evaporator. Heat engines can also be used to pump heat from colder to hotter bodies. In the fridge or air conditioner, it is the work that is costly electricity and the desired. Understand the relationship between work and heat in a cycling process follow the physics of basic heat engines and refrigerators. Refrigerators and heat pumps both operate on the same cycle. Difference between a heat engine, refrigerator and heat.

Describe the use of heat engines in heat pumps and refrigerators. Refrigerators are designed with condenser, compressor, and evaporator in one set unit, and as they push away the heat the outer surface of refrigerator is getting warm. Difference between refrigerator and heat pump 1 transfer of heat. The efficiency of the heat pump is one of the most important factors affecting to economical and energetic operation of the heat pump. To do this a heat pump must be able to absorb heat from a low temperature source. Comparison between heat engine, refrigerator, and heat. Refrigerators and heat pumps work on the same principle. Difference between ac and refrigerator 1 design of ac and refrigerator. Carnot cycle and reversed carnot cycle electrical4u. It is common to express the efficiency of the heat pump as coefficient of performance cop, which tells actually the ratio between obtained thermal energy and used work electrical energy in the compressor. Comparison between heat engine, refrigerator, and heat pump. Of course a refrigerator is a heat pump in a general meaning in many casesincluding the advanced heating and cooling system for buildingsit is exactly the same mechanism as a refrigerator, but in the technical language of thermodynamics there is an exact difference which relates to what outcome you care about see my answer.

In this mode of operation the cycle works as a refrigerator or heat pump. Fundamentals of thermalfluid sciences with student resource dvd 4th edition edit edition. What is the difference between a refrigerator and a heat pump. Oct 27, 2009 difference between a heat engine, refrigerator and heat pump heat engine in heat engine the heat supplied to the engine is converted into useful work. Heat is absorbed from this location and transferred outside, usually behind or underneath the unit where the condenser coil is located. For very high balance points small heat pumps, most of the heating is provided by auxiliary electric heat so that the scop is close to 1. Refrigerators work in reverse direction of heat engines. Energy and process engineering introduction to exergy and energy quality truls gundersen page 4 of 25 this is the background why exergy is related to ideal work. A heat pump is the opposite, to maintain a space at a high temperature by absorbing heat from a low. We see from the model, heat ql is absorbed from the lowtemperature reservoir tlconstant and heat qh is rejected to a hightemperature reservoir thconstant.

What is the difference between a refrigerator and a heat pump and a. The main difference between the two is in their operating temp. Qin wnet 1 by only 1st law violates kelvinplanck statement of 2nd law. Heat engines lecture 7 2 3 ucsd heat engine concept any time a temperature difference exists between two bodies, there is a potential for heat flow examples. Draw a carnot cycle in a ts diagram and name the processes in the cycle. Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical. Heat pumps, refrigerators, and heat engines are heat machines. The efficiencies of all reversible heat engines operating between the same two reservoirs are the same. In an absorption refrigerator, a suitable combination of refrigerant and absorbent is used. In doing so, work w r is required to be done on the system. The straight carnot cycle has led to development of the automobiles that produce the work by absorbing heat from the source and liberating remaining heat to the atmosphere. The concept of reversed heat engine has led to the development of the refrigerator and heat pump.

The reversed carnot cycle unlike the carnot heat engine, the carnot refrigeration cycle undergoes a process with opposite direction. In refrigerators working substance extracts heat q 2 from sink at lower temperature t 2. All the components of the heat pumps are same as the refrigerator and even they perform the similar functions. Coefficient of performance an overview sciencedirect topics. What is the difference between refrigerator and heat pump. In this lecture we briefly explained about how the heat engine, refrigeration.

Explain the difference between a carnot and a reversed carnot cycle p. The gas in a refrigerator can extract heat qc from the cold reservoir only if the gas temperature is lower than. A domestic refrigerator is an example of a heat pump. On the other hand, a heat pumps objective is to maintain a heated space at a high temperature. Relation between the cop of refrigerant and cop of heat. A refrigerator is essentially an insulated box with a heat pump system connected to it. The actual efficiency of this real heat engine can be obtained and compared to the. What is the difference between a refrigerator and a heat. Usually the reservoirs are assumed to be very large in size so the temperature of the reservoir remains constant regardless of the amount of heat extracted or delivered to the. Cop r,rev or cop hp,rev is the highest cop a refrigerator or a heat pump which operates between a hightemperature reservoir at temperature t h and a lowtemperature reservoir at temperature t l can reach. Comparison between coefficient of performance of heat engine, refrigerator, and heat pump. A refrigeration system cools the external fluid flowing through the evaporator, whereas a heat pump heats the external fluid flowing through the condenser. Beyond the attendant increase in your electricity bill, there is another good reason you should not try to cool the kitchen on a hot day by leaving the refrigerator door open. Thermodynamics tutorial 5 heat pumps and refrigeration on completion of this tutorial you should be able to do the following.

The cop usually exceeds 1, especially in heat pumps, because, instead of just converting work to heat which, if 100% efficient, would be a cop of 1, it pumps. A heat pump is device that transfer heat from a colder area to hotter area by using mechanical energy, as in a refrigerator. Refrigerators and heat pumps both operate on the same cycle, but they have different objectives. A heat pump can be thought of as a heat engine which is operating in reverse. Both the refrigerator and the heat pumps carry the heat from low temperature reservoir or the sink to the high temperature reservoir or source. The difference between neutral and ground on the electric panel duration. Refrigerator and heat pump a heat engine run in reverse is a refrigerator and heat pump. The evaporator coil is located inside the box, usually in the freezer compartment.

In any heat engine, heat is extracted from a hot source eg hot combustion products in a car engine. Jul 30, 2018 difference between heat pump and refrigerator, thermodynamics, physics concepts our mantra. A refrigerator maintains a space at a low temperature by removing heat from it. Feb 10, 2017 mechanical engineering channel anuniverse 22 has started to stand on the shoulders of engineering giants and now, it is a place to hang out to learn the basics of mechanical engineering. A carnot cycle for a gas engine consists of two isothermal processes and two adiabatic processes a carnot engine has max. Real air conditioners and refrigerators typically do remarkably well, having values of cop ref ranging from 2 to 6. By the end of this lesson you will be able describe the difference between a heat engine and a heat pumprefrigerator and be able to differentiate between the ef.