Apipe heater (long cylinder shape 30 mm outside diameter) is inserted through the side of a pipe in which water or air is flowing. the heater is perpendicular to fluid flow. when water with a temperature of 25°c and velocity of 1 m/s flows in the pipe over the heater, the power per unit length of the heater delivered to maintain the heater outer surface at a uniform temperature of 90°c is 28 kw/m length. when air, also at 25°c, but with a velocity of 10 m/s is flowing, the power per unit length to maintain the same surface temperature is 400 w/m. calculate and discuss comparisons between the convection coefficients for the flows of water and air. assume all of the power provided to the heater is given off as heat to the air or water.

Amass of m 1.5 kg of steam is contained in a closed rigid container. initially the pressure and temperature of the steam are: p 1.5 mpa and t 240°c (superheated state), respectively. then the temperature drops to t2= 100°c as the result of heat transfer to the surroundings. determine: a) quality of the steam at the end of the process, b) heat transfer with the surroundings. for: p1.5 mpa and t 240°c: enthalpy of superheated vapour is 2900 kj/kg, specific volume of superheated vapour is 0. 1483 m/kg, while for t 100°c: enthalpy of saturated liquid water is 419kj/kg, specific volume of saturated liquid water is 0.001043m/kg, enthalpy of saturated vapour is 2676 kj/kg, specific volume of saturated vapour is 1.672 m/kg and pressure is 0.1 mpa.

An air compression refrigeration system is to have an air pressure of 100 psia in the brine tank and an allowable air temperature increase of 60°f for standard vapor compression cycle temperatures of 77 f entering the expansion cylinder and 14 f entering the compression cylinder, calculate the coefficient of performance a. 2.5 b 3.3 c. 4.0 d. 5.0

Steam enters a converging nozzle at 3.0 mpa and 500°c with a at 1.8 mpa. for a nozzle exit area of 32 cm2, determine the exit velocity, mass flow rate, and exit mach number if the nozzle: negligible velocity, and it exits (a) is isentropic (b) has an efficiency of 94 percent