Thermodynamics Mechanical previous year questions with answer
Ques 1 GATE 2026
For an ideal gas, starting from state point 1, two different processes take place. The corresponding final states in these two processes are 2 and 3, lying on same isotherm. If P and h represent pressure and enthalpy, respectively, then which one of the following options is correct?
Ques 2 GATE 2026
For the isothermal expansion of an ideal gas in a piston cylinder system, the net heat supplied during the process is equal to the net work. Which one of the following statements is correct for the given process?
Ques 3 GATE 2026
For an ideal regenerative Rankine cycle, as shown in the figure below, which one of the following options is the correct representation of temperature-entropy (T-s) diagram?
Ques 4 GATE 2026
A liquid comes out of the reactor of a chemical plant at 250℃ temperature with a flow rate of 100 LPM. The ambient temperature is 25℃. Density and specific heat of the liquid remain constant at 1000 kg/m3 and 4.18 kJ/kg K, respectively, for the given range of temperature. The rate of exergy associated with the hot liquid stream at the exit of the plant is ________ kW (rounded off to 2 decimal places).
65.10 is the correct answer.
Ques 5 GATE 2026
A rigid closed vertical cylindrical vessel of 15 cm diameter contains 5 kg water at 80℃ with 10% quality. The water is heated till its temperature reaches 130℃. Considering only a horizontal separated interface between liquid and vapor, the dip in the liquid level after the heating process is ________ cm (rounded off to 2 decimal places).
Properties of water at various saturation temperatures are given in the table below.
| Temperature T (°C) |
Specific volume | Specific internal energy | ||
|---|---|---|---|---|
| vf (m³/kg) | vg (m³/kg) | uf (kJ/kg) | ug (kJ/kg) | |
| 80 | 0.001029 | 3.4053 | 334.97 | 2481.60 |
| 130 | 0.001070 | 0.66808 | 546.10 | 2539.50 |
25.68 is the correct answer.
Ques 6 GATE 2025
Let a spherical block of ice at -7°C be exposed to atmospheric air at 30°C with the gravitational direction as shown in the figure below. What will be the overall direction of air flow in this situation?
Ques 7 GATE 2025
Air inside a rigid, thermally-insulated tank undergoes stirring as shown in the figure below. Which one of the following options is correct?
Ques 8 GATE 2025
In a psychrometric chart, one axis represents dry-bulb temperature. The axis, that is perpendicular to the dry-bulb temperature axis, represents
Ques 9 GATE 2025
The thermal efficiency of an ideal air-standard Otto cycle is 0.5. The value of specific heat ratio of air is 1.4. The compression ratio of the cycle is ______ (rounded off to 1 decimal place).
Ques 10 GATE 2025
A thermal power plant is running with no reheat or regeneration. The specific enthalpy and specific entropy of steam at the turbine inlet are 3344 kJ kg-1 and 6.5 kJ kg-1K-1 respectively. The turbine isentropic efficiency is 0.9, and the mass flow rate of steam at the turbine inlet is 102 kg s-1. The turbine power output is ______ MW (rounded off to 1 decimal place).
Properties of saturated liquid and saturated vapor at turbine exit pressure
| Saturated liquid water | Saturated water vapor | ||
| Specific entropy (kJ kg-1K-1) | Specific enthalpy (kJ kg-1) | Specific entropy (kJ kg-1K-1) | Specific enthalpy (kJ kg-1) |
| 7.6 | 1.1 | 341 | 2645 |