CASCADE REFRIGERATION SYSTEM

Description:
A cascade system is a multistage application in which two separate refrigerant systems are interconnected in such a manner that one provides the means of heat rejection (condenser) for the other.
The lower system may, therefore may operate at a much lower temperature. Cascade system has the additional feature, over compound systems of permitting the use of different refrigerants in each cycle of the cascade.

ADVANTAGES:

  1. The principal advantage of the cascade system is that, it permits the use of two or more different refrigerant, thus each refrigerant circuit is comparatively simple.
  2. Each refrigerant can be chosen that operates best within the required comparatively narrow temperature and pressure range. For example, a refrigerant, which does require a vacuum in the evaporator to produce a low suction temperature, is selected for the low stage system. Another refrigerant such as R-404 A, which does not require an excessive pressure in the condenser, is selected for use in the high stage system.
  3. As each cycle is operating separately, there is no difficulty of lubrication.
  4. The refrigerants used in the system will have successively low freezing temperatures, so that refrigerants having low freezing point can be used in high temperature circuit and refrigerant having high freezing point can be used in the low temperature circuit.
  5. Inclusion of inter-cooling with liquid refrigerants in the cascade system improves the performance of the system.

PRINCIPLE OF OPERATION:

Cascade system is just similar to the binary vapour cycle used for the power plants. In the Binary vapour cycle a condenser for mercury works as a boiler for water.
Similarly, in the cascade system the condenser for low temperature cycle works as an evaporator for the high temperature cycle.
In a cascade system, a series of refrigerants with progressively lower freezing points is used in the series of single stage unit.

CONSTRUCTION:

All the components of cascade system are mounted on the powder coated fabricated stand. The cascade system is divided in the three parts. These are as follows: High side ,Intermediate stage and Low side.
The cascade system consist of hermetically sealed compressors, shell and coil type condenser, desuper-heater, water flow cut-out, expansion device, expansion chamber, cascade condenser, oil-Seperator, and low-side evaporator.
The refrigerant used on the high side is R -404a, and the refrigerant used on the low side is SUVA-95.
On the high side a hermetically sealed compressor, shell and coil type condenser, drier/filter, flow meter, expansion device, and cascade condenser are connected to each other.
On the low side a hermetically sealed compressor, oil Separator, De-super heater, cascade condenser, drier/filter, expansion device, low side evaporator, expansion chamber, cooling fan are connected with each other.
Separate pressure gauges are provided to measure the pressure at the compressor inlet and compressor outlets. HP/LP cutout is used as a safety device.
Cooling thermostats are provided in the cascade condenser and in the low side evaporator. Separate energy-meters are provided to measure the energy consumed by the compressor and the heater. A dimmer is also provided to control the input of the heater. Flow meter in the liquid line is incorporated to measure the refrigerant flow. Digital temperature indicator displays temperatures at various locations as per the selection viz. temperature before and after compressor and before and after expansion.

WORKING:

Initially, when the compressor is started, the refrigerant is compressed at high pressure, and then it enters into the shell and coil type condenser, where the flowing water absorbs all the heat. Then it enters into the drier/filter, flow meter and it goes into the expansion device where its expansion takes place and pressure drops. Then it enters into the cascade condenser where it takes heat from the low side refrigerant (SUVA-95)
In the low side system compressor discharges refrigerant at high pressure, then it enters into the oil separator where compressor oil gets separated from the refrigerant. Then refrigerant goes into de-super heater where its heat gets absorbed by flowing water, then it goes into cascade condenser (i.e., high side evaporator) where its heat is rejected and it becomes in liquid form. After passing through drier /filter, expansion device it goes into low side evaporator where it absorbs heat from chamber. It converts into low-pressure vapour state. Then it goes into the compressor. SUVA-95 is having high standing pressure so it becomes trouble for compressor starting. So to avoid it refrigerant is stored in the expansion chamber where the pressure takes place. It is connected in series with the compressor inlet line.

Technical Specifications:

SUB-TITLE PARAMETER HIGH SIDE LOW SIDE
MODEL AECS-01
REFRIGERATION SYSTEM Refrigerant R 404A / R-22 SUVA-95 / R-23
Temp. attained -30 Deg Celsius Low side chamber at -80 deg C
Evaporation temperature -40 Deg Celsius -90 Deg Celsius
Corresponding suction pressure 05 psig 05 psig.
Condensing temperature +35 Deg Celsius - 30 Deg Celsius
Discharge pressure 350 psig 120 psig
Discharge gas temperature 48 Deg Celsius -35 Deg Celsius
Desuperheater NA Required
Compressor Hermetically sealed, Emerson/ Danfoss or equivalent Hermetically sealed, Emerson/ Danfoss or equivalent
Compressor oil Standard Standard
Oil separator NA Danfoss-OUB-1
Condenser Water Cooled Cascade condenser- tube in tube type/ PHE type
Drier DM-50 DM-50
Evaporator Tube-in-tube / Plate type heat exchanger Forced convection air cooled
Expansion device Thermostatic expansion valve Capillary Tube
Accumulator Copper / M.S. shell suction line accumulator provided.
Insulation 65 MM PUF 250 MM PUF
CONTROLS & INDICATIONS HP/LP Cutout Provided Provided
Temperature Digital Indicator with selector Digital Indicator with selector
Pressure Pressure gauges 2 Nos. for suction and discharge Pressure gauges 2 Nos. for suction and discharge
ELECTRICAL SYSTEM Supply 415 volts, 3 phase, 50 Hz
Input power 5.0 kW
Rated current 8.0 Amps.
Energy-meters Provided for compressor. Provided for compressor and heater
CONSTRUCTION Outer body 1.2 thk CRCA, powder coated
Inner body Stainless steel.
Size 2750x775 x1340 mm (L*D*H)

Specifications subject to change without any notification.

List Of Experiments:

  1. To evaluate the cooling capacity of cascade system.
  2. To evaluate actual and theoretical C.O.P. of Cascade Refrigeration system.
  3. To plot the actual Refrigeration Cycle on P-H and T-S charts.
  4. To study various components and controls used in Cascade Refrigeration system.

Rating conditions * : Ambient temperature= 35o C, atmospheric pressure = 1.01 bar,

CUSTOMER SCOPE:

  1. A CONTINUOUS WATER SUPPLY OF 50 LPM@2.5 BAR AT AMBIENT TEMPERATURE OR A COLING TOWER OF 5 TR CAPACITY.
  2. ELECTRICAL POWER POINT 415 VOLTS, 50 HZ, 3 PH, WITH 32 AMPS MCB.
  3. CLEAR SPACE OF 3MTR X 2 MTR.

 

cascade refrigeration system-Jagajeet Marketing