List of top Thermodynamics Questions on Laws of thermodynamics

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

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 \(R=287~\mathrm{J\,kg^{-1}\,K^{-1}}\).]

At which of the following locations in the atmosphere is the anvil of a towering cumulonimbus cloud usually located?
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)}
Air in an ideal Diesel cycle is compressed from 3 litre to 0.15 litre. It then expands during a constant pressure heat addition process to 0.3 litre. If the ratio of specific heats, \(\gamma = 1.4\), the thermal efficiency (in %) of the cycle is ..................... (rounded to one decimal place).
The inlet and outlet temperatures of the flowing fluid during a steady state flow process are the same as that of the surroundings. If the changes in kinetic and potential energies are neglected, the maximum power that can be obtained is equal to
A heat engine having thermal efficiency of 40% receives heat from a source at \(600 \, K\) and rejects heat to a sink at \(300 \, K\). The second-law efficiency (in %) of this engine is .................. (answer in integer).
If \(\gamma\) refers to the ratio of specific heats, the air-standard efficiency of an Otto cycle is
A tank is divided into two compartments with one compartment containing a gas at a given pressure, while the second is completely evacuated. If the partition is removed, the gas occupies the entire compartment. Which one of the following statements is CORRECT?
A cylindrical tank containing water is rotating about the z-axis at a constant angular velocity of 10 rad s$^{-1}$. The schematic of the isobaric surface is shown below, where ‘A’ and ‘B’ are two points on the isobaric surface at heights $z_1$ and $z_2$, respectively. Assuming negligible atmospheric pressure and no transient flow, estimate the elevation difference in m between $z_1$ and $z_2$. (Given: $r_1 = 0.5 \, m$, $r_2 = 1.0 \, m$, $g = 9.8 \, m/s^2$, $\omega = 10 \, rad/s$).
There are 295 million vehicles across India driving about 12000 km yr$^{-1}$. Each vehicle consumes about 25 km l$^{-1}$ of petrol, and the amount of carbon released per litre is 5.5 g. What is the amount of carbon emitted into the atmosphere in mega tons per year?
Two parallel isobars are separated by 250 km at 30°N with air density = 0.70 kg/m$^3$, Coriolis parameter $f = 2\Omega \sin \phi$ (where $\Omega = 14.6 \times 10^{-5}$ rad/s), and pressure gradient = 5 hPa. Calculate the geostrophic velocity in m/s.
If $D_{10}$ for {Salmonella} in egg yolk is 0.75 kGy, calculate the radiation dose in kGy (rounded off to 2 decimal places) required for reducing the {Salmonella} count in egg yolk by 8 log cycles.
The average moisture binding energy of a plant protein-based snack at 8% moisture content (dry basis) is 3200 cal.mol$^{-1}$. If the water activity of the snack at the above moisture content is 0.30 at 30°C, the water activity of the sample at 45°C is ............. (rounded off to 2 decimal places). Use $R = 1.987$ cal.mol$^{-1}$.K$^{-1}$.
Cow milk is pasteurized at a flow rate of 1 kg.s$^{-1}$ in a counter-current heat exchanger using hot water as the heating medium. The milk enters at 15°C and exits at 50°C. The specific heat of milk is 3.5 kJ.kg$^{-1}$.°C$^{-1}$. Hot water enters at 75°C and exits at 60°C. Overall heat transfer coefficient $U = 1800$ W.m$^{-2}$.°C$^{-1}$. Find the heat transfer surface area in m$^2$ (rounded off to 2 decimal places). Assume steady-state.
The typical speeds of a tsunami wave in water depths of 10 m, 100 m, and 1000 m, respectively, are ................
A piston–cylinder device initially contains $1 \, m^3$ of air at $200 \, kPa$ and $25^\circ C$. Air expands at constant pressure while a heater of $250 \, W$ is switched on for 10 minutes. There is a heat loss of $4 \, kJ$. Assuming air as an ideal gas, the final temperature of air is $____________________$ $^\circ C$ (rounded off to one decimal place). Given: $R = 0.287 \, kJ/kgK$, $c_p = 1.005 \, kJ/kgK$.
The following statements are given: (i) The third law of thermodynamics deals with the entropy of a substance at the absolute zero temperature.
(ii) Entropy of any non-crystalline structure is zero at absolute zero temperature.
(iii) At the absolute zero temperature, the crystal structure has maximum degree of order.
(iv) The thermal energy of the substance at absolute zero temperature is maximum.
The correct option describing these statements is:
Adiabatic bulk modulus of a substance is defined as:
A rigid tank contains $2 \, kg$ of an ideal gas at $500 \, kPa$ and $350 \, K$. A valve is opened and half of the gas is released. Then valve is closed. Final pressure = $300 \, kPa$. Find final temperature $T_2$ (in K).
If an ideal air-standard Otto cycle and an ideal air-standard Diesel cycle operate on the same compression ratio, then the relation between thermal efficiencies ($\eta_{th}$) of the cycles is: