This untreated warm moist air will impose an additional refrigeration load and must be taken into account in the heat load calculation. It is also an ideal textbook for graduate and senior undergraduate students in mechanical, chemical, biochemical, industrial and food engineering disciplines. Ppt refrigeration cycles powerpoint presentation free. Winner of the standing ovation award for best powerpoint templates from presentations magazine. The refrigeration cycle can be broken down into the following stages see figure 4. Cascading improves the cop of a refrigeration cycle. Basic refrigeration cycle nina sri maulani 121624023 tptu 2012 2.
Wet refrigeration cycle the expander has been substituted by a throttling valve. Cascade cycle is used where a very wide range of temperature between tl and th is required. These principles are applied to various practical systems, including heat engines, refrigeration cycles, air conditioning, and chemical reacting systems. The chilled water circulating through the cooling coil tubes, after picking up heat from the mixed air, leaves the cooling coil and goes through the chilled water return chwr pipe to the chillers evaporator.
Heat rejection from the lower cycle to the upper cycle takes place in an. But they all face the same issues relating to both condensation control and moisture. The groups also represent the four phases of designing a refrigeration system. Pdf textbook of refrigeration and air conditioning by r. The absorption refrigeration cycle is an alternative that absorbs the refrigerant in a liquid solution rather than evaporating it. Horizontal lines on the ph chart are lines of constant pressure and vertical lines are lines of constant enthalpy or heat energy. Ph diagram representation of a dry refrigeration cycle. The reversed carnot cycle consumes a fraction of the net work area 1a3b but produces a greater amount of refrigeration triangular area under b1. For 30 years, topics such as air refrigeration cycles and systems, vapour. The main components there are four main components in a refrigeration system. It is also used in domestic and commercial refrigerators, largescale. Proceedings of the 3rd international conference on fluid flow, heat and mass transfer ffhmt16 ottawa, canada may 2 3, 2016 paper no.
Download textbook of refrigeration and air conditioning by r. Khurmi is very useful for mechanical engineering mech students and also who are all having an interest to develop their knowledge in the field of design, automobile, production, thermal engineering as well as all the works related to mechanical field. Refrigeration cycles the vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. A i t f 200 250 212 100 sensible steam heat measurable temperature temperature above 212 f. University of california, berkeley department of mechanical. When 1 pound of ice melts, it absorbs 144 btu, as latent energy. The refrigeration cycle is a critical component of hvac systems and is governed by the principles of thermodynamics. Refrigeration systems refer to the different physical components that make up the total refrigeration unit. Coolpack tutorial page 6 the group eescooltools contains a large collection of programs for both refrigeration systems and components. So refrigeration cycle should be known to understand the refrigeration system. Before we dive in, lets get an understanding of four key concepts. Refrigeration systems cover a broad spectrum of application temperatures and environments, many of which are discussed in the 2006 ashrae handbookrefrigeration.
Refrigeration cycle is the basis of all refrigeration systems. A thermodynamic refrigeration cycle removes heat from a lowtemperature object refrigeration and rejects it at a higher temperature. Vapor compression refrigeration system basic, working, parts of system, advantages, and disadvantages introduction. The rate of refrigeration, the net power input, and the cop are to be determined. These systems consist of an evaporator, a condenser, a compressor and an expansion valve.
Thus a heat pump may be thought of as a heater if the. This article describes what is refrigeration, and common methods of refrigeration like ice refrigeration and dry ice refrigeration. Ph diagram representation of a dry refrigeration cycle refrigerant fluid choice. Commercial refrigeration is concerned with the designing, installation, and maintenance of refrigerated fixtures of the type used by retail stores, restaurants, hotels, and institutions for the storing, displaying, processing, and dispensing of perishable commodities of all types. An ejector refrigeration system can perform much better under the high evaporator temperatures shown in fig. Mechanical refrigeration works by changing the the majority of heat is removed from the the majority of the works by removedchanging the absorbed heat is state of the refrigerant. Comparison of system cop for various refrigerants at t g 80c, t c 35c and t e 5c. Worlds best powerpoint templates crystalgraphics offers more powerpoint templates than anyone else in the world, with over 4 million to choose from. Theyll give your presentations a professional, memorable appearance the kind of sophisticated look that todays audiences expect. Remembering that the stirling cycle is a totally reversible cycle, the reversed stirling cycle is. Khurmi a textbook of refrigeration and air conditioning is an aptly written textbooks for the students of mechanical engineering while also a mustread for anyone with an interest in the subject. The primary difference is in the manner in which heat is utilized. Vaporcompression refrigeration, in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for airconditioning of buildings and automobiles.
Comparative study of the performance of an ejector. Refrigeration calculations pressureenthalpy charts are tools to use in better understanding refrigeration cycles, for judging whether the operation is normal, and for estimating the effect of change in operation. Chapter 9 gas power cycles universiti tenaga nasional. Vapor compression refrigeration system basic, working. A comparative study has been carried out of r12, 22, 125, 4a, 152a, 218, 245, 500, 502, 507 and 717 as working fluids in a vapourcompression refrigeration system. Consider a twostage cascade refrigeration system operating between the pressure limits of 0. Usually, one tends to pick pl as low as possible, but not below atmospheric. Textbook of refrigeration and airconditioning written by r. Most of the differences between the ideal and the actual cycles are because of the irreversibilities in various components which are. A heat pump is a mechanical system that allows for the transference of heat from one location the source at a lower temperature to another location the sink or heat sink at a higher temperature. Thermodynamic cycles can also be categorized as gas cycles or vapor cycles, depending on the phase of the working fluidthe substance that circulates through the cyclic device. The challenge in refrigeration and air conditioning is to remove heat from a low temperature source and dump it at a higher temperature sink. It is a compression process, whose aim is to raise the refrigerant pressure, as it flows from an evaporator.
The gas refrigeration cycles have lower cops relative to the vaporcompression refrigeration cycles or the reversed carnot cycle. Each stage operates on an ideal vapor compression refrigeration cycle with refrigerant4a as the working fluid. Some basic refrigeration cycles are discussed here through different diagrams. This cyclic process requires that work be input so that. Refrigeration system an overview sciencedirect topics. This type of refrigeration system is very popular in recreational vehicles as well as in remote locations where electrical power is not readily available. When the gas is throttled from very high pressure to low pressure in the throttling valve, its temperature reduces suddenly while its enthalpy remains constant. Spark ignition gasoline engines, compression ignition diesel engines and conventional gas turbine engines generally refer to as internal combustion engines or ic engines are. We want to design a vaporcompression refrigeration cycle to absorb heat from a cool environment and reject it to a warm environment. Types of insulation for refrigeration applications. This is the amount of heat required to turn a liquid into a gas. The design is to be based upon the ideal vaporcompression refrigeration cycle, with four components. Since moisture is a good thermal conductor, its presence in an insulation system is highly detrimental. Refrigeration is defined as the science of maintaining the temperature of a particular space lower than the surrounding space.
Sep 10, 2016 the refrigeration cycle is a critical component of hvac systems and is governed by the principles of thermodynamics. The cooled supply air leaves the cooling coil and the air cycle repeats. Refrigeration systems and applications, third edition is an indispensable working resource for researchers and practitioners in the areas of refrigeration and air conditioning. Refrigeration systems and applications wiley online books. Thermodynamically, when the body at certain temperature is kept in the atmosphere it tends to attain the temperature of the atmosphere. List salient points of various refrigeration techniques, and. Learning how to read the charts and to do the calculations involved will pay rich dividendsin all phases of refrigeration work. Khurmi by textbook of refrigeration and airconditioning. Refrigeration fundamentals heatcraft worldwide refrigeration. The vapor compression refrigeration cycle involves four components. Solve problems based on the otto, diesel, stirling. The purpose of a refrigerator is the removal of heat, called the cooling load, from a lowtemperature medium. This section of the course is devoted to describing the basic fundamentals of how various heat engines work e.
Zubair latif comsats institute of information technology, lahore 2. Whats going on inside the system depends on the purpose of the cycle. Power cycles otto cycle spark ignition diesel cycle. Look at different cycles that approximate real processes you can categorize these processes several different ways power cycles vs. 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. The four types of refrigeration systems you need to know. Actual refrigeration cycles are not as efficient as ideal ones like the carnot cycle because of the irreversibilities involved. The vapor compression refrigeration cycle, step by step. Refrigeration is the process of heat removal from a low temperature sink and added to a high temperature reservoir to. So hopefully you see why refrigeration is an important topic. Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pumps and refrigerators. The compressor the condensing coil the metering device the evaporator 3.
Most refrigeration cycles are typically represented by a pressureenthalpy ph diagram, which shows the phase changes of the refrigeration cycle and provides a graphical means of study. The highpressure refrigerant flows through a condenserheat exchanger before attaining the initial. This is often measured at the liquids boiling point. The different stages in the refrigeration cycle are undergone in these physical systems. Refrigeration fundamentals 2175 west park place blvd. Gas power cycles deal with systems that produce power in which the working fluid remains a gas throughout the cycle in other words, there is no change in phase. If an expander had been used the line from d to a would be a vertical line. Course prerequisites chemistry 1a, mathematics 1b, physics 7b, and engineering 7 textbooks andor other required material. The above figure shows the objectives of refrigerators and heat pumps. Gas refrigeration cycles include the reversed brayton cycle and the hampsonlinde cycle. Introduction a major application area of thermodynamics is refrigeration, which is the transfer of heat from a lower temperature region to a higher temperature one. Gas refrigeration cycle objectives and content objectives.
Evaluate the performance of gas power cycles for which the working fluid remains a gas throughout the entire cycle. We have chosen to divide this group into four subgroups as shown on figure 2. Refrigeration selection guide air change or ventilation load each time a door is opened to a refrigerated room from an adjacent unrefrigerated space, some outside air will enter the room. Compression refrigeration cycles in general take advantage of the idea that highly compressed fluids at one temperature will tend to. Understanding of various configurations of ejector cycles. You probably recall the three types of cycles from lesson 4f, but it has been a while. Just as the vapors are used for cooling in the vapor compression cycle and vapor absorption cycle, the gas is used for cooling in gas refrigeration cycle. The refrigeration cycles can also be represented in a ph diagram. In this chapter, we will discuss practical refrigeration and heat pump cycles and the refrigerants used within these cycles. In the past, this was done by collecting ice in the winter and using its specific heat to cool as the ice melted. Refrigeration systems operate on a series of consecutive thermodynamic processes that form a cycle that returns the working substance to the same state. Develop simplifying assumptions applicable to gas power cycles.
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