A house is heated in winter by a biogas boiler. The boiler is rated at 70,000 Btu/h. The heating value of biogas is 13,000 Btu/h and the average boiler efficiency is 87 percent. Taking the total win- ter period to be 3000 hours and assuming that the boiler operates at an average load of 75 percent, determine the amount of biogas consumed in therm (1 therm = 100,000 Btu) in the winter season. If the biogas is sold at a unit price of $1.20/therm, determine the cost of this biogas to the homeowner.

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.

The temperature of air decreases as it is compressed by an adiabatic compressor. a)- true b)- false

Acompressor receives the shaft work to decrease the pressure of the fluid. a)- true b)- false