List of top Thermodynamics Questions

The directions of the South Pacific Subtropical Gyre and the North Atlantic Subtropical Gyre are ________________ and ________________, respectively.
Air enters a hair dryer at 22 °C and 100 kPa with a velocity of 3.7 m/s, and leaves the dryer at 83 °C and 100 kPa with a velocity of 9.1 m/s. The exit area of the dryer is 18.7 cm\(^2\), and the ambient temperature is 22 °C. The air is an ideal gas with gas constant \(R = 0.287 \, kJ/kg\!-\!K\) and isobaric specific heat \(c_p = 1.005 \, kJ/kg\!-\!K\). If the change in potential energy is neglected, the second law efficiency (in %) of the dryer is ..................... (rounded off to one decimal place).
Consider a gas obeying the relation \[ P(v - b) = RT \] where \(b\) and \(R\) are constants. Which of the following statement(s) is/are CORRECT about the specific heat capacity at constant pressure?
A rigid tank of 300 litre capacity contains 3 kg of oxygen (molar mass = 32 kg/kmol) at \(25^\circ C\). If oxygen behaves as an ideal gas, the pressure (in kPa) inside the tank is ............... (rounded off to two decimal places). Use: \(R_u = 8.314 \, kJ/kmol-K\)
Let \(T_H\) and \(T_L\) denote the absolute temperatures of high and low temperature reservoirs, respectively. The coefficient of performance (COP) of a reversible refrigerator operating between these two reservoirs is
A closed system undergoes a process 1–2 in which it absorbs 150 kJ of energy as heat and does 90 kJ of work. Then it follows another process 2–3 in which 80 kJ of work is done on it while it rejects 60 kJ as heat. If it is desired to restore the system to the initial state (state 1) by an adiabatic path, the work interaction (in kJ) in this process will be
A cylinder of volume \(0.1 \, m^3\) is filled with nitrogen at \(10 \, MPa\) and \(300 \, K\). Consider nitrogen to be an ideal gas. The cylinder develops a leak and nitrogen escapes to the atmosphere which is at \(0.1 \, MPa\). After some time, the pressure in the cylinder reduces to \(5 \, MPa\). Assuming the cylinder and the leaked gas temperature remains constant at \(300 \, K\), the work done (in MJ) by nitrogen gas is:

Consider that specific heat (0 to \(50~^\circ\mathrm{C}\)) of water, water vapour and air remains constant: \(4.48\), \(1.88\) and \(1.0~\mathrm{kJ/(kg\^\circ C)}\), respectively. Assuming the heat energy required to convert \(1~\mathrm{kg}\) of water to water vapour at \(0~^\circ\mathrm{C}\) is \(2000~\mathrm{kJ}\), the enthalpy (in kJ/kg dry air) of atmospheric air containing \(0.05~\mathrm{kg}\) water vapour per kg dry air at \(50~^\circ\mathrm{C}\) is ________. (rounded off to 1 decimal place)

A hot-air balloon (volume \(1000~\mathrm{m^3}\)) with gross mass (envelope, basket, payload; excluding the air inside) \(100~\mathrm{kg}\) is in hydrostatic balance. External air: \(T_\text{out}=10^\circ\mathrm{C}\), \(\rho_\text{out}=1~\mathrm{kg\,m^{-3}}\). The temperature of the air inside the balloon is ________ \(^\circ\mathrm{C}\). (Round off to the nearest integer)

In hot weather, a human body cools by evaporation of sweat. The amount of water that must evaporate to cool the body by \(1~^\circ\mathrm{C}\) is __________________________% of the body mass. (Round off to two decimal places) 
[Given: latent heat of vaporization of water \(L_v=2.25\times10^6~\mathrm{J\,kg^{-1}}\); specific heat capacities of body and water \(c=4.2\times10^3~\mathrm{J\,kg^{-1}\,K^{-1}}\).]

One kg of dry air at \(15~^\circ\mathrm{C}\) is isothermally compressed to one–tenth of its initial volume. The work done on the system is ______________________________________ kJ. (Round off to the nearest integer) [Use the gas constant for dry air \(R=287~\mathrm{J\,kg^{-1}\,K^{-1}}\).]

Which of the following Period(s) correspond(s) to wind waves?
At which of the following locations in the atmosphere is the anvil of a towering cumulonimbus cloud usually located?
Which one of the following is the main reason why tropical cyclones rarely form over the Bay of Bengal during the summer monsoon season?
The time period of the inertial oscillation at a location R is 1.5 times that of a particle moving at a speed of \(0.5~\mathrm{m/s}\) at a location S (87°E, 45°S). Which of the following is the latitude of location R? (Round off to the nearest integer)
Which one of the following is the main cause of the land-sea temperature contrast that drives phenomena like sea breeze and the Indian summer monsoon?
A fruit juice is concentrated using an ultrafiltration membrane. A feed stream at \(10~\mathrm{kg/min}\) with \(6%\) total solids (by weight) is increased to \(20%\) total solids (by weight). The membrane tube has \(10~\mathrm{cm}\) inside diameter and the pressure difference across the membrane is \(2000~\mathrm{kPa}\). If the permeability constant of the membrane is \(5 \times 10^{-6}\ \mathrm{kg\ water/(m^2\ kPa\ s)\), the length of membrane tube (in m) is \underline{\hspace{2cm}}. (rounded off to 2 decimal places)}
In a typical grinding operation, \(80%\) of the feed material passes through a sieve opening of \(4.75~\mathrm{mm}\); whereas, \(80%\) of the ground product passes through \(0.5~\mathrm{mm}\) opening. If the power required to grind \(2~\mathrm{tonnes/h}\) of the feed material is \(3.8~\mathrm{kW}\), the work index of the material is \underline{\hspace{2cm}. (rounded off to 2 decimal places)}
During which of the following times of the day is the 2 m air temperature usually the lowest at a tropical location?
In a piston-cylinder assembly, one kmol of an ideal gas is compressed from an initial state of 200 kPa and 400 K to a final state of 1 MPa and 400 K. If the surroundings are at 400 K, the minimum amount of work (in kJ/kmol) required for the compression process is ............... (rounded off to two decimal places). Use: Universal gas constant (\(R_u\)) = 8.314 kJ/kmol-K
Two Carnot heat engines (E1 and E2) are operating in series as shown in figure. Engine E1 receives heat from a reservoir at \(T_H = 1600 \, K\) and does work \(W_1\). Engine E2 receives heat from an intermediate reservoir at \(T\), does work \(W_2\), and rejects the rest to a reservoir at \(T_L = 400 \, K\). Both the engines have identical thermal efficiencies. The temperature \(T\) (in K) of the intermediate reservoir is ............ (answer in integer).
A particular temperature scale is obtained according to the relation: \[ t = a e^{\alpha} + b \] where \(a\) and \(b\) are constants, and \(t\) is in °C. The thermometric property as measured by the thermometer is \(\alpha\). The values of \(\alpha\) at ice point and steam point are 6 and 9, respectively. The temperature (in °C) which gives \(\alpha = 7\) is ................. (rounded off to two decimal places).
A steam boiler contains saturated water vapour at 200 °C. After a certain period, the temperature of the boiler drops to 110 °C. Assume that all the valves of the boiler are closed and the energy is lost as heat to the surroundings. The ratio of mass of liquid to the mass of vapour is ............. (rounded off to two decimal places). Data: - \(v_g(200^\circ C) = 0.127 \, m^3/kg\) - \(v_g(110^\circ C) = 1.210 \, m^3/kg\) - \(v_f(110^\circ C) = 0.001 \, m^3/kg\)
A stream of superheated steam (2 MPa, 300 °C) mixes with another stream of superheated steam (2 MPa, 400 °C) through a steady-state adiabatic process. The flow rates of the streams are 3 kg/min and 2 kg/min, respectively. This mixture then expands in an adiabatic nozzle to a saturated mixture with quality of 0.77 and 1 kPa. Neglect the velocity at the nozzle entrance and the change in potential energies. The velocity at the nozzle exit (in m/s) is ............ (rounded off to two decimal places). Data given: - At 2 MPa, 300 °C: \(h = 3024.2 \, \text{kJ/kg}\) - At 2 MPa, 400 °C: \(h = 3248.4 \, \text{kJ/kg}\) - At 1 kPa: \(h_f = 29.3 \, \text{kJ/kg}, h_{fg} = 2513.7 \, \text{kJ/kg}\)
A piston-cylinder assembly having 250 mm diameter contains 0.01 kg of water vapor at 1 MPa and 200 °C. The specific volume of the vapor is 0.20602 m³/kg. The system expands as per the relation \(pV^n = \text{constant}\), where \(n\) is the polytropic exponent. The expansion of water vapour displaces the piston by 50 mm. If the final pressure is 0.35 MPa, the value of the exponent \(n\) is ................ (rounded off to two decimal places).