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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 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 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

 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 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

(0) A l-in.-OD steel tube has its outside wall surface maintained at 250°F. Itis proposed that the rate of heat transfer be increased by adding fins b. in. thick and iin. long to the outside tube surface. Compare the increase in heat transfer achieved by adding 12 longitudinal .straight fins against that achieved by adding

Heat is to be transferred from water to air through an aluminum wall. It is proposed that rectangular fins 0.05 in. thick and I in. long and spaced 0.08 in. apart be added to the aluminum surface to aid in transferring heat. The heat transfer coefficients on the air and water sides are 3 Btu/hr-ft2-~F

Attributes of the inlet streams to a heat exchanger are as follows: The product in Btu/hr- OF for the heat exchanger is given by where eh and e are the capacities in Btu/lir-E Using only s-NTU method, (a) Find the outlet temperatures and rating for a parallel-flow arrangement. (b) Find the outlet temperatures and rating for a

A 0.25-in.thick steel wall contains 0.125-in. diameter by OJ-in. long copper spines located on 0.37S-in. center-to-center spacing. The spine fins are placed in a square array. The heat transfer coefficient on the side of the wall without fins is 1,000 Btu/hr-ft2-°F. Devise a computer solution to calculate the value of UA for a 1_ft2section of