Problem 1: In a food processing plant a brine solution is heated from 6^oC to 12^oC in a double-pipe heat exchanger by water entering at 50^oC and leaving at 40^oC at the rate of 0.166 kg/s. If the overall heat transfer coefficient is 850 W/m2-oC, what heat exchanger area is required for-

(a) What heat exchanger area is required for parallel flow?

(b) What heat exchanger area is required for counter flow?

Problem 2: A double-pipe, parallel flow heat exchanger uses oil (c_p = 1.88 kJ/kg-^oC) at an initial temperature of 205^oC to heat water, flowing at 225 kg/h, from 16^oC to 44^oC. The oil flow rate is 270 kg/h.

(a) What heat exchanger area is required for an overall heat transfer coefficient of 340 W/m²-^oC?

(b) Determine the number of transfer units (NTU).

(c) Calculate the effectiveness of the heat exchanger.

Problem 3: a) Estimate the heat transfer from a 40 W incandescent bulb at 127^oC to 27^oC quiescent air. Approximate the bulb as a 50 mm diameter sphere.

b) What percentage of the power is lost by free convection?

Problem 4: Air at 27^oC flows normal to a 77^oC, 30 mm outside diameter water pipe. The air moves at  1.0 m/s.

(a) Estimate the heat transfer per unit length.

Problem 5: Consider atmospheric air at 25^oC and a velocity of 25 m/s flowing over both surfaces of a 1-m long flat plate that is maintained at 125^oC.

1. Determine the rate of heat transfer per unit width from the plate for values of the critical Reynolds number corresponding to 10₅, 5x10₅, and 10₆.

Problem 6: A shell-and tube heat exchanger (two shells, four tube passes) is used to heat 10,000 kg/h of pressurized water from 35 to 120^oC with 5000 kg/h pressurized water entering the exchanger at 300^oC.

(a) If the overall heat transfer coefficient is 1500 W/m²-K, determine the required heat exchanger area.