1.It's proposed to have a water heater that consists of an insulated pipe of 5-cm diameter and an electric resistor inside. Cold water at 20oC enters the heating section steadily at a rate of 30L/min. If water is to be heated to 55oC, determine
A.) the power rating of the resistance heater and
B.) the average velocity of the water in the pipe.
2.A liquid R-134a bottle has an internal volume of 0.001 m3 . initially it contains 0.4 kg of R-134a (saturated mix) at 26oC. A valve is opened and R-134a vapor only is allowed to escape slowly such that temperature remains constant until the mass of R-134a remaining is 0.1kg. find heat tranfer necessary with the surroundings to maintain the temperature and pressure of R-134a constant.