1. Why is the effectiveness ~of a heat exchanger a good measure of the amount of energy that could be exchanged from two streams at different temperatures? 2. Are fins constructed from a low-k or a high-k material more effective? Explain. 3. Are fins more effective when added to a high- he or a low- […]

1. Is a parallel or counter flow heat exchanger more effective for a given area? Why? 2. What is the difference in accuracy between the LMTD method and the NTU method? 3. CDlin/Cma

In a single-pass counter flow heat exchanger, 10,000lbmlhr of water (C = 1.0 Btu/ibm-F) enters at 60°F and cools 20,000 lbm/hr of oil (C = 0.5 Btu/Ibm-OF),which enters at 200°F. For the exchanger, UA = 5,500 Btu/hr- “E Determine the fluid outlet temperatures.

Compressed air is used in a heat-pump system to heat water that is subsequently used to warm a house. The house demand is 95,000 Btu/hr. Air enters the exchanger at 200’F and leaves at 120’F; water enters and leaves the exchanger at 90’F and 125’F,respectively. Choose, from the following alternatives, the unit that is most

Water enters a counter flow, double-pipe heat exchanger at a rate of70 kg/min and is heated from 1ST to 60’C by an oil with a specific heat of 1.9 kJ/kg-K. The oil enters at 116’C and leaves at 27’C. The overall heat transfer coefficient is 300 W/m2 -K. (a) What heat transfer area is required? (b)

Water at 300’F and 8 ftls enters a 50-ft-Iong schedule 40 I-in. cast-iron pipe. If air at 32’F flows perpendicularly to the pipe at 40 ft/s, determine (a) the outlet temperature of the water, (b) the outlet water temperature if the air velocity is increased to 160 ft/s, (c) the outlet water temperature if the

Water at 300’F and 8 ftls enters a 50-ft-Iong schedule 40 I-in. cast-iron pipe. If air at 32’F flows perpendicularly to the pipe at 40 ft/s, determine (a) the outlet temperature of the water, (b) the outlet water temperature if the air velocity is increased to 160 ft/s, (c) the outlet water temperature if the

A double-pipe heat exchanger with the dimensions shown in Fig. P2-9 is used to heat water (Tin = 50°F). Steam at 250’F is condensing on the outside with an ho = 2,500 Btu/ft2-hr-‘F. Sufficient steam is available. If the water flow rate is 3 ft/s, find the outlet temperature of the water. Neglect the thermal

 Heat is to be transferred from an unknown fluid to air through an aluminum wall. It is proposed that rectangular fins 1.2 mm thick and 6.35 mm long be added to the surface to increase the heat transfer. The fins will be spaced 2.0 mm apart. The wall is 3 mm thick and the air-side

A pipe with circumferential fins has the dimensions given in Fig. P2-11. On the outside, a gas with the following properties is flowing: On the inside, a liquid has the following properties: Compute the pipe length required to cool the liquid to 180°F