In a facility, a counter-flow double-pipe heat exchanger is used to cool the fluid at a flow of 10.0 kg / s (Cp = 3.15 kJ / kgK) with an inlet temperature of 90 0C, and the surface area of the heat exchanger is As = 9 m2. The refrigerant (Cp = 4.2 kJ / kgK) enters the heat exchanger at a temperature of 10 ° C and a flow rate of 8.0 kg / h. Total heat transfer coefficient according to system data; ? = equation is given image. a) Calculate the heat transfer and heat exchanger exit temperatures. b) Existing heat exchanger is wanted to be changed. A seller offers an attractive discount to the plant authorities for two heat exchangers of the same property with a surface area of As = 5 m2. Since the pipe diameters in existing and new heat exchangers are the same, it is expected that the total heat transfer coefficient equation given above will also be valid for new heat exchangers. The vendor suggests that both heat exchangers can be operated in parallel in a counter-flow fashion, so that each new heat exchanger can operate at half the mass flow rates for hot and cold fluids, and this new situation can meet the needs of the facility. Evaluate the proposal by making the necessary calculations.
Heat Exchangers
Heat exchangers are the types of equipment that are primarily employed to transfer the thermal energy from one fluid to another, provided that one of the fluids should be at a higher thermal energy content than the other fluid.
Heat Exchanger
The heat exchanger is a combination of two words ''Heat'' and ''Exchanger''. It is a mechanical device that is used to exchange heat energy between two fluids.
In a facility, a counter-flow double-pipe heat exchanger is used to cool the fluid at a flow of 10.0 kg / s (Cp = 3.15 kJ / kgK) with an inlet temperature of 90 0C, and the surface area of the heat exchanger is As = 9 m2. The refrigerant (Cp = 4.2 kJ / kgK) enters the heat exchanger at a temperature of 10 ° C and a flow rate of 8.0 kg / h. Total heat transfer coefficient according to system data; ? = equation is given image.
a) Calculate the heat transfer and heat exchanger exit temperatures.
b) Existing heat exchanger is wanted to be changed. A seller offers an attractive discount to the plant authorities for two heat exchangers of the same property with a surface area of As = 5 m2. Since the pipe diameters in existing and new heat exchangers are the same, it is expected that the total heat transfer coefficient equation given above will also be valid for new heat exchangers. The vendor suggests that both heat exchangers can be operated in parallel in a counter-flow fashion, so that each new heat exchanger can operate at half the mass flow rates for hot and cold fluids, and this new situation can meet the needs of the facility. Evaluate the proposal by making the necessary calculations.
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