A heating system must maintain the interior of a building at TH = 20°C when the outside temperature is TC = 10°C. If the rate of heat transfer from the building through its walls and roof is 15 kW, determine the electrical power required, in kW, to heat the building using: (a) electrical-resistance heating; (b) a heat pump whose coefficient of performance is 4; (c) a reversible heat pump operating between hot and cold reservoirs at 20°C and 10°C, respectively.

On a average work day more than work place firs are reorted

Ajournal bearing has a journal diameter of 3.250 in with a unilateral tolerance of 20.003 in. the bushing bore has a diameter of 3.256 in and a unilateral tolerance of 0.004 in. the bushing is 2.8 in long and supports a 700-lbf load. the journal speed is 900 rev/min. find the minimum oil film thickness and the maximum film pressure for both sae 20 and sae 20w-30 lubricants, for the tightest assembly if the operating film temperature is 160°f. a computer code is appropriate for solving this problem.

Air flows over a heated plate àt a velocity of 50m/s. the local skin factor coefficient at a point on a plate is 0.004. estimate the local heat transfer coefficient at this point. the following property data for air are given: density = 0.88kg/m3 , viscosity 2.286 x 10 ^-5 kgm/s , k = 0.035w/mk ,cp = 1.001kj/kgk. use colburn reynolds analogy.