Thermodynamics important questions bank

 This post help you for the mechanical engineering student who is going to write thermodynamics exam.Here important repeated 2 marks and 16 marks of unit 1 is given. 

Anna University Chennai

Regulation 2013

                                     Thermodynamics                 

                                              UNIT-5   Part - A

                                     Answer all the questions             

1. Define degree of saturation. 

2. Differentiate absolute humidity and relative humidity.

3. Define dew point depression.

4. What is meant by adiabatic saturation temperature?

5. What is psychrometer? 

6.What is humidification and dehumidification?

7. Define sensible heat and latent heat.

8. What are the important psychrometric processes?

9. State Helmholtz function.

10. What are the assumptions made in Vanderwaal’s equation of state? 

                                                  Part - B                 

1. 30 m3/ min of moist air at 15 C DBT and 13 C WBT are mixed with 12m3/min of moist air at 25 C DBT and 18 C WBT. Determine DBT and WBT of the mixture assuming the barometric pressure is one atmosphere. 

2.For the atmospheric air at room temperature of 30 C and relative humidity of 60% Determine partial pressure of air, humidity ratio, dew point temperature, density and enthalpy of mixture.

3. Atmospheric air at 1.0132 bar has a DBT of 32◦C and a WBT of 26◦C. Find (i) the partial pressure of water vapour (ii)the specific humidity (iii) the dew point temperature (iv) the relative humidity (v) the degree of saturation (vi)the density of the air in the mixture (vii) the density of the vapour in the mixture (viii) the enthalpy of the mixture. 

4. One kg of ice at -5 C is exposed to atmosphere which is at 20 C. The ice melts and comes into contact into thermal equilibrium with the atmosphere. (i)  Determine the entropy increase of the universe. (ii) What is the minimum amount of work necessary to convert the water back into ice at -5 C? Cp of ice is 2.093 kJ / kg K and the latent heat of fusion of ice.

5.A sample of moist air at 1 atm and 25 C has a moisture content of 0.01% by volume. Determine  the  humidity  ratio,  the  partial  pressure  of  water  vapour,  the  degree  of saturation, the relative humidity and the dew point temperature.

6. Air at 20 C, 40% R.H is mixed with air at 40 C, 40% R.H in the ratio of (former) 1:2 (later) on dry basis. Determine the final condition of air.

7. One kg of air at 40 C dry bulb temperature and 50% relative humidity is mixed with 2 kg of air at 20 C dry bulb temperature and 20 C dew point temperature. Calculate the temperature and specific humidity of the mixture. 

8.  Determine the rate of power loss due to irreversibility in a heat engine operating between temperatures of 1800 K and 300 K. Engine delivers 2 MW of power when heat is added at the rate of 5 MW. 

9. An air-water vapour mixture enters an air- conditioning unit at a pressure of 1.0 bar, 38 C DBT, and a relative humidity of 75%. The mass of dry air entering is 1 kg/s. The air- vapour mixture leaves the air-conditioning unit at 1.0 bar, 18 C, 85% relative humidity. The moisture condensed leaves at 18 C. Determine the heat transfer rate for the process. 

10. Atmospheric air at 1.0132 bar has 20 C DBT and 65% RH. Find the humidity ratio, wet bulb temperature, dew point temperature, degree of saturation, enthalpy of the mixture, and density of air and density of vapour in the mixture. 

11. In a laboratory test, a sling psychrometer recorded dry bulb and wet bulb temperatures as 303 K and 298 K respectively. Calculate (i) vapour pressure (ii) relative humidity (iii) specific humidity (iv)Degree of saturation (v) dew point temperature (vi) enthalpy of the mixture. 

12.1 kg of air at 40 C DBT and 50% relative humidity is mixed with 2 kg of air at 20 C DBT and 20 C dew point temperature. Calculate the specific humidity, enthalpy and the dry bulb temperature of the mixture.