IMPROVEMENT of COP USING FLASH CHAMBER

Introduction The mechanism used for lowering or producing low temp. in a body or a space, whose temp. is already below the temp. of its surrounding, is called the refrigeration system. Here the heat is being generally pumped from low level to the higher one & is rejected at high temp.

In vapour compression refrigeration system, When refrigerant (generally in liquid state due to rejection of latent heat in condenser coil) is passed through expansion valve in which pressure and temperature drops during which some amount of refrigerant in liquid form converts in vapour (generally termed as Flashing).

If this vapour is sent along with low temperature refrigerant into evaporator, efficiency decreases due to reduction of contact surface between liquid refrigerant and evaporator internal surface reducing the overall efficiency of system.To improve the efficiency of evaporator coil only liquid refrigerant has to be sent by separating it from vapour.Flash chamber separates liquid from vapour refrigerant and sends only liquid refrigerant to evaporator and vapour to compressor by bypassing evaporator coil.

COMPONENTS REQUIREDCompressor(Reciprocating-Godrej/Tecunesh/Emersion)-1/8 or1/6 hpCondenser (Dynamic condenser) Capacity 100lts/165 ltrExpansion valve Freezer Box- 60 ltr capacity Capillary tube copper capillary tube ( 0.31/0.36mm inside bore,length- 9 ft)

ContdDryer cum Filter copper dryer/ DM50Relay Electrical relayOverload ProtectorThermostat switchRefrigerant-134aFlash chamber

ContdCopper TubeCompressor discharge to condenser inlet) inch outside bore, 2 ft lengthCondenser outlet to dryer - inch outside bore, 1 ft lengthEvaporator outlet to compressor suction inch outside bore, 4 to 5 ft lengthCompressor charging inch outside bore, 1 ft length

Contd.Charging ValveRubber mounting bush -4 nos with 4 nos nut & boltHolding boxControlling unit(using microcontroller)

Refrigerator & Refrigerant A refrigerator is a reversed heat engine or a heat pump which takes out heat from a cold body & delivers it to a hot body.

The refrigerant is a heat carrying medium which during their cycle in a refrigeration system absorbs heat from a low temp. system & delivers it to a higher temp. system.

ContdHere we are using hydrocarbon as refrigerant, which is eco friendly and does not harm ozone layer.

The refrigerant used here is R134a

CompressorAreciprocating compressororpiston compressoris apositive-displacement compressorthat usespistonsdriven by acrankshaft to deliver gases at high pressure.In our project we use reciprocating compressor of Godrej with 1/6 hp.

How it Works

ContdThe intake gas enters the suction manifold, then flows into the compression cylinder where it gets compressed by a piston driven in a reciprocating motion via a crankshaft, and is then dischargedReciprocating compressors are typically used where high compression ratios (ratio of discharge to suction pressures) are required per stage without high flow rates, and the process fluid is relatively dry.

Dynamic CondenserCost efficient wire-on-tube construction Optimized for airflow and space constraints Supports clean-back designIdeal for large capacity systems In our project we use 165 lt dynamic condenser

Expansion ValveThermostatic expansion valve or TEV is one of the most commonly used throttling devices in the refrigerator and air conditioning systems.

The thermostatic expansion valve is the automatic valve that maintains proper flow of the refrigerant in the evaporator as per the load inside the evaporator

ContdIf the load inside the evaporator is higher it allows the increase in flow of the refrigerant and when the load reduces it allows the reduction in the flow of the refrigerant. This leads to highly efficient working of the compressor and the whole refrigeration and the air conditioning plant.

Capillary TubeCapillary tubes are the most simple refrigerant metering device used in air conditioners and other refrigeration equipment.

There are no moving parts, just a very small diameter tube that meters refrigerant from the high side into the cooling coil.

Here we use copper capillary tube ( 0.31/0.36mm inside bore length- 9 ft)

Contd. The total amount of heat being rejected to the outside body consist of two parts:-

- the heat extracted from the body to be cooled .

- the heat equivalent to the mechanical work required for extracting it.

Flash chamber

Flash chamber is used in between expansion valve and evaporator.To improve the efficiency of evaporator coil only liquid refrigerant has to be sent by separating it from vapour. Flash chamber separates liquid from vapour refrigerant and sends only liquid refrigerant to evaporator and vapour to compressor by bypassing evaporator coil.

Flash chamber

Refrigeration SystemsVapour compression refrigeration system

Vapour absorption refrigeration system

Thermo electric refrigeration system

Contd.Each cycle of operation consists of the four fundamental changes of state or processes:- ExpansionVaporisationCompressionCondensation

Compressor The low pressure & temp. refrigerant from evaporator is drawn into the compressor through the inlet or suction valve , where it is compressed to a high pressure & temp.

The high pressure & temp vapour refrigerant is discharged into the condenser through the delivery or discharge valve.

Condenser

The condenser or the cooler consists of coils of pipe in which the high pressure & temp. vapour refrigerant is cooled & condensed.

The refrigerant while passing through the condenser, rejects its latent heat to surrounding condensing medium which is normally air or water.

Thus hot refrigerant vapour received from compressor is converted into liquid form in condenser.

Receiver The condensed liquid refrigerant from the condenser is stored in a vessel, known as receiver, from where it is supplied to the expansion valve or refrigerant control valve.

Expansion Valve The function of this valve is to allow the liquid refrigerant under high pressure & temp. to pass at a controlled rate after reducing its pressure & temp.

some of liquid refrigerant evaporates as it passes through the expansion valve, but the greater portion is vaporised in the evaporator at the low pressure & temp.

Evaporator An evaporator consists of coils of pipes in which the liquid vapor refrigerant at low pressure & temp. is evaporated & changed into vapor refrigerant at low pressure & temp.

During evaporation process, the liquid vapor refrigerant absorbs its latent heat of vaporization from the medium which is to be cooled.

RefrigerantCFCs(R-11, R-12, R-502) and HCFCs(R-22s) deplete ozone layer once exposed to air which in turn harmful to all form of life.

The alternative refrigerant to be used is 1. Hydrofluro carbons(HFCs) 2. Hydrocarbons(HCs)

HFCs are non flammable and environmental friendly with zero ozone depletion potential, but it is difficult to use.

Hydrocarbons are generally environmental friendly and easy to use. There are two types of HCs. a. R-600a b. A blend of propane/isobutane(each 50% by weight) c. R-290

In our project we will use blend of propane and iso butane as a refrigerant.

The advantage of using the above refrigerant is it is free of global warming and depletion of ozone layer.

This refrigerant is highly flammable and could be used easily with some protection measures.

AdvantagesSmaller size for a given refrigerating capacityHigher coeff. of performanceLower power requirements for a given capacity Less complexity in both design & operationIt can be used over large of temp.

Domestic RefrigeratorThe application of refrigeration for domestic purposes are mainly in the form of domestic refrigerators & home freezers.

The main purpose of this type of refrigeration is to provide low temp. for storage & distribution of foods & drinks.

Contd.It represents a significant portion of the refrigeration industry due to the use of these units in large number.For domestic preservation, the storage is generally short term. The domestic refrigerators used for the purposes are usually small in sizes with rating in ranges from 1/20 to tonne.

Contd.The unit is usually self contained and hermetically sealed.

Due to short term storage the domestic refrigerator load is intermittent.

Contd.dependable and without any necessity of expert inspection & repair.

Non irritant & non toxic refrigerant should be used.

Generally methylene chloride, freon-12, freon -11 are used as refrigerants.

Contd.The heat of the bodies to be cooled is carried to the evaporator coils by means of air trapped in the cabinet.Refrigeration is not only provided with double walled cabinet packed with materials having high thermal insulation such as fibre glass or expanded rubber but also all around the inside of door flap soft rubber seal is used which makes rubber air tight.

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