Second Law of Thermodynamics
Practice QuestionsMarks 1
1
Air inside a rigid, thermally-insulated tank undergoes stirring as shown in the figure below. Which one of the following options is correct?
GATE ME 2025
2
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).
GATE ME 2025
3
A furnace can supply heat steadily at 1200 K at a rate of 24000 kJ/min. The maximum amount of power (in kW) that can be produced by using the heat supplied by this furnace in an environment at 300 K is
GATE ME 2024
4
A heat engine extracts heat (𝑄H) from a thermal reservoir at a temperature of 1000 K and rejects heat (𝑄L) to a thermal reservoir at a temperature of 100 K, while producing work (𝑊). Which one of the combinations of [𝑄H, 𝑄L and 𝑊] given is allowed?
GATE ME 2023
5
The Clausius inequality holds good for
GATE ME 2022 Set 1
6
A heat pump absorbs $$10$$ $$kW$$ of heat from outside environment at $$250$$ $$K$$ while absorbing $$15$$ $$kW$$ of work. It delivers the heat to a room that must be kept warm at $$300$$ $$K.$$ The Coefficient of performance $$(COP)$$ of the heat pump is _____________.
GATE ME 2017 Set 1
7
The heat removal rate from a refrigerated space and the power input to the compressor are $$7.2$$ $$kW$$ and $$1.8$$ $$kW$$, respectively. The coefficient of performance $$(COP)$$ of the refrigerator is ___________
GATE ME 2016 Set 2
8
The $$COP$$ of a Carnot heat pump operating between $${6^ \circ }C$$ and $${37^ \circ }C$$ is ____________
GATE ME 2015 Set 2
9
A Carnot engine $$(CE$$-$$1)$$ works between two temperature reservoirs $$A$$ and $$B,$$ where $${T_A} = 900K$$ and $${T_B} = 500K.$$ A second Carnot engine $$(CE$$-$$2)$$ works between temperature reservoirs $$B$$ and $$C,$$ where $${T_c} = 300\,\,K.$$ In each cycle of $$CE$$-$$1$$ and $$CE$$-$$2,$$ all the heat rejected by $$CE$$-$$1$$ to reservoir $$B$$ is used by $$CE$$-$$2.$$ For one cycle operation, if the net $$Q$$ absorbed by $$CE$$-$$1$$ from reservoir $$A$$ is $$150$$ $$MJ,$$ the net heat rejected to reservoir $$C$$ by $$CE$$-$$2$$ (in $$MJ$$) is ______________
GATE ME 2015 Set 1
10
A reversed Carnot cycle refrigerator maintains a temperature of $$ - {5^ \circ }C.$$ The ambient air temperature is $${35^ \circ }C.$$ The heat gained by the refrigerator at a continuous rate is $$2.5$$$$kJ/s.$$ The power (in watt) required to pump this heat out continuously is _____________.
GATE ME 2014 Set 4
11
The following four figures have been drawn to represent a fictitious thermodynamic cycle, on the $$P$$-$$v$$ and $$T$$-$$S$$ plates
According to the first law of thermodynamics, equal areas are enclosed by
GATE ME 2005
12
An industrial heat pump operates between the temperatures of $${27^ \circ }C$$ and $$ - {13^ \circ }C.$$ The rates of heat addition and heat rejection are $$750$$ $$W$$ and $$1000$$ $$W,$$ respectively. The $$COP$$ for the heat pump is
GATE ME 2003
13
Consider a refrigerator and a heat pump working on the reversed Carnot cycle between the same temperature limits. Which of the following is correct?
GATE ME 1995
14
In the case of a refrigeration system undergoing an irreversible cycle, $$\oint {{{SQ} \over T}} $$ is _____________$$\left( { < 0/ = 0/ > 0} \right)$$
GATE ME 1995
15
Any thermodynamic cycle operating between two temperature limits is reversible if the product of efficiency when operating as a heat engine and the coefficient of performance when operating as a refrigeration is equal to $$1.$$
GATE ME 1994
16
A reversible heat transfer demands:
GATE ME 1993
17
A condenser of a refrigeration system rejects heat at a rate of $$120$$ $$kW,$$ while its compressor consumes a power of $$30$$ $$kW.$$ The coefficient of performance of the system would be
GATE ME 1992
Marks 2
1
A heat pump, operating in reversed Carnot cycle, maintains a steady air temperature of 300 K inside an auditorium. The heat pump receives heat from the ambient air. The ambient air temperature is 280 K . Heat loss from the auditorium is 15 kW . The power consumption of the heat pump is __________ kW (rounded off to 2 decimal places).
GATE ME 2025
2
A heat pump (H.P.) is driven by the work output of a heat engine (H.E.) as shown in the figure. The heat engine extracts 150 kJ of heat from the source at 1000 K. The heat pump absorbs heat from the ambient at 280 K and delivers heat to the room which is maintained at 300 K. Considering the combined system to be ideal, the total amount of heat delivered to the room together by the heat engine and heat pump is _______kJ (answer in integer).
GATE ME 2024
3
In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to evaporator is ________.
GATE ME 2022 Set 2
4
A reversible cycle receives $$40$$ $$kJ$$ of heat from one heat source at a temperature of $${127^ \circ }C$$ and $$37$$ $$kJ$$ from another heat source at $${97^ \circ }C.$$ The heat rejected (in $$kJ$$) to the heat sink at $${47^ \circ }C$$ is ___________
GATE ME 2016 Set 2
5
A reversible heat engine receives $$2$$ $$kJ$$ of heat from a reservoir at $$1000$$ $$K$$ and a certain amount of heat from a reservoir at $$800$$ $$K$$. It rejects $$1$$ $$kJ$$ of heat to a reservoir at $$400$$ $$K.$$ The net work output (in $$kJ$$) of the cycle is
GATE ME 2014 Set 1
6
A heat transformer is a device that transfers a part of the heat, supplied to it at an intermediate temperature, to a high temperature reservoir while rejecting the remaining part to a low temperature heat sink. In such a heat transformer, $$100kJ$$ of heat is supplied at $$350$$ $$K.$$ The maximum amount of heat in $$kJ$$ that can be transferred to $$400K,$$ when the rest is rejected to a heat sink at $$300K$$ is
GATE ME 2007
7
An irreversible heat engine extracts heat from a high temperature source at a rate of $$100kW$$ and rejects heat to a sink at a rate of $$50kW.$$ The entire work output of the heat engine is used to drive a reversible heat pump operating between a set of independent isothermal heat reservoirs at $${17^ \circ }C$$ and $${75^ \circ }C$$. The rate (in $$kW$$) at which the heat pump delivers heat to its high temperature sink is
GATE ME 2007
8
A heat engine having an efficiency of $$70\% $$ is used to drive a refrigerator having a coefficient of performance of $$5.$$ The energy absorbed from low temperature reservoir by the refrigerator for each $$kJ$$ of energy absorbed from high temperature source by the engine is
GATE ME 2004
9
A solar collector receiving solar radiation at the rate of $$0.6$$$$kW/{m^2}$$ transforms it to the internal energy of a fluid at an overall efficiency of $$50\% $$. The fluid heated to $$350$$ $$K$$ is used to run a heat engine which rejects heat at $$313$$ $$K.$$ If the heat engine is to deliver $$2.5$$ $$kW$$ power, then minimum area of the solar collector required would be
GATE ME 2004
10
A Carnot cycle is having an efficiency of $$0.75.$$ If the temperature of the high temperature reservoir is $${727^ \circ }C,$$ what is the temperature of low temperature reservoir?
GATE ME 2002
11
A cyclic heat engine does $$50$$ $$kJ$$ of work per cycle. If the efficiency of the heat engine is $$75\% $$, then heat rejected per cycle is
GATE ME 2001
12
For two cycles coupled in series, the topping cycle has an efficiency of $$30\% $$ and the bottoming cycle has an efficiency of $$20\% $$. The overall combined cycle efficiency is
GATE ME 1996
13
A solar energy based heat engine which receives $$80$$ $$kJ$$ of heat at $${100^ \circ }C$$ and rejects $$70$$ $$kJ$$ of heat to the ambient at $${30^ \circ }C$$ is to be designed. The thermal efficiency of the heat engine is
GATE ME 1996
14
Round the clock cooling of an apartment having a load of $$300$$ $$MJ/day$$ requires and air-conditioning plant of capacity about
GATE ME 1993