Question

A 10-m-long countercurrent-flow heat exchanger is being used to heat a liquid food from 20 to 808C. The heating medium is oil, which enters the heat exchanger at 1508C and exits at 608C. The specific heat of the liquid food is 3.9 kJ/(kg K). The overall heat-transfer coefficient based on the inside area is 1000 W/ (m2 K). The inner diameter of the inside pipe is 7 cm. a. Estimate the flow rate of the liquid food. b. Determine the flow rate of the liquid food if the heat exchanger is operated in a concurrent-flow mode for the same conditions of temperatures at the inlet and exit from the heat exchanger.

Answer 1

mlf=0.5038kg/s

Step-by-step explanation:

a. Please kindly check attachment for the step by step solution

b. B) in concurrent flow heat exchanger same exit temperatures for both fluids cannot be obtained. Since tho<tco

Case ii) only liquid food is considered tci=20 &tco=80

Cp=3.9kj/kgk

&If Q is same then mlf=0.5038kg/s this is same as case a