Problem 1

An experimentalist claims to have raised the temperature of water from room temperature to 150oC using saturated steam at 200 kPa. Evaluate his claim based on Second law of thermodynamics.

Problem 2

Solar energy stored in large bodies of water called solar ponds is being used to generate electricity. If such a solar power plant has an efficiency of 4% and a net power output of 350 kW, find the average value of the required solar energy collection rate in Btu/hr.

Problem 3

An air conditioning system is used to maintain a house at 75oF while the outside is at 95oF. The house is gaining heat through walls and windows at a rate of 800 Btu/min and heat generation rate within the house from people and appliances is 100 Btu/min. Determine the minimum power input required for this air conditioning system.

Problem 4

A cup of hot coffee at 75oC can only lose heat to the room at 25oC and come in thermodynamic equilibrium with atmosphere. Explain this using the Principle of increase in entropy of universe. Assume heat capacity of coffee to be 3.9 kJ/kg-K.

Problem 5

Find the change in entropy of 1 kg of air if its temperature and pressure are doubled in the process.

70. In a gas-fired boiler, water is boiled at 145 degrees celcius by hot gases flowing through a stainless steel pipe submerged in water. If the rate of heat transfer from the hot gases to water is 81.04 kJ/s, determine the rate of evaporation of water.