A small space heater is constructed of 1.25 cm, 18-gauge brass tubes that are 60 cm. The tubes are arranged in equilateral, staggered triangles on 3.6 cm centers with four rows of 15 tubes each. A fan blows 0.95 m³/s of atmospheric pressure air at

21°C uniformly over the tubes (see sketch). Estimate
(a) The heat transfer rate

(b) The exit temperature of the air

(c) The rate of steam condensation assuming that saturated steam at 15 kPa (abs) inside the tubes is the heat source. State your assumptions. Work parts (a), (b), and (c) of this problem by two methods: first use the LMTD, which requires a trial-and-error or graphical solution, then use the effectiveness method.

Transcribed Image Text:

Air 3.6 cm Duct wall 2- 2 31 3 4 I י ד - 60 cm 22