Methods of Refrigeration: Literature Review


2.1 Introduction

In survey of applied thermo kineticss all the piece we have been detecting heat transportation from a system at higher temperature to that at lower temperature. Now in the survey of infrigidation we will be detecting assorted methods of chilling the objects and keeping the temperature of organic structures at values lower than environing temperature.

Harmonizing to American society of Heating, Refrigeration and Air-conditioning Engineers ( ASHARE ) “Refrigeration is the scientific discipline of supplying and keeping temperature below that of the surrounding ( ambient ) temperature” .

In the olden yearss around 2500 old ages B.C. Indians, Egyptians, etc. , were bring forthing ice by maintaining H2O in the porous stations open to cold atmosphere during the dark period. The vaporization of H2O in about cool dry air accompanied with recitative heat transportation in the clear dark caused the formation of ice even when the ambient temperature was above the freezing temperature. Further mentions are available which support the usage of ice inChina1000 old ages BC. Nero, the emperor, was utilizing ice for chilling drinks. Further, the East Indians were able to bring forth infrigidation by fade outing salt in H2O every bit early as 4Thursdaycentury A.D. , of class, on really little graduated table. The usage of evaporative chilling is another application of infrigidation used olden yearss. The chilling of H2O in earthen pots for imbibing intent ; is the most common illustration where the vaporization for H2O through the pores of earthen pot is accompanied with chilling of H2O.

The bow said methods of the production of chilling were non executable for the commercial usage due to really little sum of ice production. Availability of natural ice in limited parts and inaccessibility of good quality insularity confined the application of ice to those vicinities merely. These all led to the development of unreal infrigidation side, a few would be presented here. Thomas Harris and John Long got the earliest British parent in 1790. Later on in 1834 Jacob Perkins developed manus operated infrigidation system utilizing ether ( volatile ) as the working fluid. Ether vapour is sucked by the non-automatic compressor and so high temperature and force per unit area either vapour is condensed in the H2O cooled chamber ( capacitor ) . Liquid quintessence is eventually throttled to the lower force per unit area, and therefore vaporization of this liquid in chamber A lowers the temperature of H2O environing the vas. Finally ice is formed. In this system, ether is used once more and once more in the cyclic procedure with negligible wastage.

In 1851, Dr. John Garrie ofFlorida, a doctor obtained the first American patent of a cold air machine to bring forth ice in order to bring around people enduring from the high febrility. Alternatively of air or quintessence, sulfuric quintessence was used by Dr. James Harrison ofAustraliain 1860, the world’s first installing of infrigidation machine for brewery. The steam engine works as a power beginning which drives the compressor for the pressurization of sulfuric quintessence vapour, which is, in bend, condensed and is allowed to spread out and vaporize in order to bring forth infrigidation. Dr. Alexander Kirk ofEnglandconstructed a cold air machine is 1861 similar to that of Dr. Gorrie. The air was compressed by a reciprocating compressor driven by a steam engine running on coal. His existent machine consumed about 1 kilograms of coal to bring forth 4 kilogram of ice ( about ) .

In the 19Thursdaycentury, there was enormous development of infrigidation systems to replace natural ice by unreal ice bring forthing machines. Unfortunately steam engine, a really low velocity power developing beginning, was used to drive the compressor, rendering really hapless public presentation of the infrigidation system.

Some Recent Promotions of in Refrigeration

In the beginning of 20Thursdaycentury, big sized infrigidation machines were under advancement. By 1904 about 450 ton chilling system for air conditioning the New York Stock Exchange was installed. InGermanypeople used air conditioning in theater for comfort intents. In around 1911 the compressor velocity was raised between 100 to 300 revolutions per minute. The first two-stage modem compressor was brought under usage in 1915.

During the civil war there was an acute deficit of the supply of natural ice from the North. Hence, Ferdinand Care of theUSAdeveloped vapour-absorption infrigidation system ammonium hydroxide as a refrigerant and H2O as a absorbent. The system consists of an evaporator, an absorber, a pump, a generator, a capacitor and an enlargement device. The evaporated vapour is absorbed by the weak ammonia-water mixture in the absorber giving strong greenish blue ammonium hydroxide. The pump delivers this strong solution into the generator where heat transportation from a burner separates ammonia vapour and the weak ammonium hydroxide H2O returns to the absorber. On the other manus the ammonium hydroxide vapour condenses in the capacitor before being throttled. The throttled ammonium hydroxide liquid enters the evaporator ensuing in completion of the cyclic procedure.

In the beginning of two decennaries of the 20th century, the development in infrigidation system was confined to refinement in cold air machines and vapor compaction thermoelectric, pulse tubing infrigidation systems, etc. The developments are vortex tubing, steam-jet infrigidation system, handiness of stuffs of specific belongingss for thermoelectric stuffs. The possible usage of waste heat or solar energy in instance of vapor-absorption and thermoelectric systems has led to development of several commercial units these yearss particularly due to the similar goon of future energy crisis, the universe is traveling to face.

A capacitor is a heat money changer is which de-superheating of high temperature vapour changes the stage from vapour to liquid and stand in chilling of condensate occurs. The capacitor is an of import device used in the high force per unit area side of a infrigidation system. Its map is to take heat of hot vapour refrigerant discharged from the compressor. The hot vapourrefrigerating consists of the heat absorbed by the evaporator and the heat of compaction added by the mechanical energy of the compressor motor. The heat from the hot vapour refrigerant in a capacitor is removed foremost by reassigning it to the walls of the capacitor tubings and so from the tubings to the condensation or chilling medium. The chilling medium may be air or H2O or a combination of the two. An air cooled capacitor is one in which the remotion of heat is done by air. It consists of steel or Cu tube through which the refrigerant flows. The size of tubing normally ranges from 6mm to 18mm outside diameter, depending upon the size of the capacitor. Generally Cu tubings are used because of its first-class heat transportation ability. The capacitors with steel tubings are used in ammonia refrigerating systems. Majority of the domestic iceboxs uses the natural convection air cooled capacitor. The present work icebox uses the natural convection air cooled capacitor. In natural convection air cooled capacitor, the heat transportation from the capacitor coils to the air is by natural convection. As the air comes in contact with the warm capacitor tubings, it absorbs heat from the refrigerant and therefore the temperature of air additions. The warm air being lighter, rises up and cold air from below rises to take away the heat from the capacitor. This rhythm continues in natural convection air cooled capacitors. This work is an experimental attack to increase the heat to be rejected in the capacitor every bit good as addition the public presentation of the system. If the capacitor is holding more fives spacing so the figure of fives available at the capacitor are less. Due to this surface country decreases. Therefore less heat transportation occurs. On the other manus if the capacitor is holding less fives spacing so the figure of fives available at the Capacitors are more. Therefore more heat rejection takes topographic point in the capacitor. Because of more heat rejection bomber chilling occurs at the issue of the capacitor which in bend increases the public presentation of the system.

Decreasing energy ingestion and increasing efficiency is one of the most of import points in our epoch. Becoming a affair of primary importance in air conditioning, industrial and commercial chilling applications, supermarket chilling, blast freeze and procedure chilling applications, energy efficiency affects design ofhair-raisers ( and its equipment such ascapacitors, compressors etc. ) and urges makers to develop high public presentation, energy-efficient, environment friendly, economic, and long life merchandises.

Becoming a affair of primary importance in air conditioning, industrial chilling, supermarket chilling, commercial chilling, blast freeze and procedure chilling applications, etc. , energy efficiency affects the design of hair-raisers that account for a important ratio of the energy ingestion in workss. Legal statute laws that for the short tally bound, and in the long tally prohibit the usage of fluids of high planetary warming possible, that are damaging to the ozone bed are besides influential on designs. Since air cooled capacitors are among the indispensable constituents of chilling groups, attempts to better their energy efficiency are made endlessly, the related national and international criterions are upgraded and restrictions on their energy ingestions are ever increasing.

Our statement will convey –in the visible radiation of the latest applicable standards- elaborate and comparative information on applications aimed at bettering the energy efficiency in air cooled capacitors, foregrounding the importance of energy efficiency in chilling installings.

2.2 The consequence of condensation temperature on capacity

The condensation temperature of the refrigerant is considered to be 6°C – 20°C above air recess temperature for general intents. The condensation temperature varies harmonizing to the ambient temperature in which the system will run. This said, the condensation temperature for applications is normally taken as 30-60°C.

Factors taken into consideration for finding the condensation temperature

  1. Ambient temperature,
  2. Thermo physical belongingss of the refrigerant,
  3. Properties of the selected compressor and
  4. The dimensions of the capacitor.

While supplying the nominal capacitor capacity in capacitors as per the Euro vent Standard, the air recess temperature and condensation temperature are taken as 25°C and 40°C severally. In other words, T = 15 °C.

A low value should be selected for the temperature differential T, in topographic points of high ambient temperature. For case, while planing for the conditions of Antalya the T value should be selected within the scope of 7° – 10° C. For systems that will run in out-of-door environments in conditions of Turkey, the temperature derived function should be lowered as one goes from the North to the South and choices should be made consequently. It must ever be considered that High Compression Temperature creates a burden on the compressor that reduces efficiency and shortens its utile life. It will be rather good in the design for the condensation temperature to be specified every bit low as possible. However, in some conditions it is non possible to take a low value for the condensation temperature. For illustration in Middle East states where the out-of-door temperature is 50°C-55°C, high capacitor temperature is ineluctable.

The undermentioned illustration shows the compressor absorbed power at assorted condensation temperatures and the achieved chilling capacities for a semi-hermetic type HGX4/555-4 theoretical account compressor manufactured by BOCK, which uses R134A gas. The chilling gas selected for the illustration is R134A. As seen from the tabular array, when the condensation temperature rises from 30°C to 60°C, the compressor draws 25 % more power while the chilling capacity beads by 38.5 % , the COP value lessenings by 51 % and the a unit that is 38.5 % larger must be used to accomplish the chilling capacity declared in the design.

2.3 Tried and True for Millennia

Copper tube has been in usage by civilisation for 1000s of old ages, and it has been found present in the H2O lines of Ancient Egypt.

Contemporary houses holding Cu pipes installed 70 old ages ago are still working good in the present twenty-four hours and necessitate far less to repair and modify than alternate methods. Should you take Cu, you will hold really small care, whereas even unstained steel Begins to corrode over clip, particularly if it is non painted or coated.

There are a great assortment of utilizations for Cu tube. If you invest a high grade into Cu, you may be able to easy repossess your investing with high rates of return for reuse and recycling for illustration. Copper is a antic renewable resource because it is easy recycled.

Beneficial Qualities of Copper Tubing

  1. Proven Longevity
  2. Comparably Lightweight
  3. Immune to Corrosion
  4. Can Be Formed to Determine
  5. Largely Nontoxic and Non Carcinogenic

2.4 Copper Condenser Coils

Capacitors are one of the outstanding utilizations of Cu tube. Changing gases into liquids occur at appropriate temperature dew point. Copper ‘s antic heat transportation rates are one of the best picks for accomplishing this end, transcending other heat transportation tubing stuffs ( such as aluminium in this instance ) by about 800 % while keeping a strong, lightweight construction. Having a higher heat transportation rate renders less entire stuff necessary for a given infinite, leting for more compact, lightweight, and simple capacitor applications that minimize back force per unit area. CTCG builds capacitors with Cu tube, aluminium tube, and unstained steel tube, to client prints — but we extremely recommend Cu tube for capacitor applications.

2.5 All Designs Accepted for Review

Whether your spiral is, snaky, coaxal, or wholly customized, all designs are accepted for reappraisal. Both difficult drawn andannealed, flexible Cu tubeacceptable for organizing and gyrating. Easily outsource production tallies of usage Cu tubing spirals or purchase bulk tonss of usage and non-custom length Cu tube, including degree lesion spirals, H2O tube and piping, infrigidation tube, DWV and capillary tube.

Supplying Tubing Coils for Most Industries

Copper meets many industries ‘ highest criterions for excellence; therefore we recommend the usage of Cu for your applications in

  1. The Aerospace Industry,
  2. Construction Industry,
  3. Freon Recycling Industry,
  4. Medical Industry, and the
  5. AC & A ; Refrigeration Industry

Most undertakings can be easy manufactured, including such points as gas turbines, artistic undertakings, diagnostic hardware,in one to four hebdomads( and sometimes faster ) . Check our present stock list to see what tube types can be serviced this month

2.6 Why Copper

Copper tube is the ideal stuff for many applications. Its strength, the easiness with which it is fabricated and soldered, and its high conduction to heat is priceless in the procedure of edifice places and industrial edifices, peculiarly for the infrigidation and air conditioning equipment installed.

Tubing made from Cu is one of the few naturally-sourced stuffs that are 100 % reclaimable, so no metal is lost in repossessing Cu from pipes no longer needed, doing it a good pick for the hereafter.

July 26, 2017