1
GATE ME 2014 Set 3
Numerical
+2
-0
An amount of $$100$$ $$kW$$ of heat is transferred through a wall in steady state. One side of the wall is maintained at $${127^ \circ }C$$ and the other side at $${27^ \circ }C$$. The entropy generated $$($$in $$W/K)$$ due to the heat transfer through the wall is _____________
2
GATE ME 2012
MCQ (Single Correct Answer)
+2
-0.6
An ideal gas of mass $$m$$ and temperature $${T_1}$$ undergoes a reversible isothermal process from an initial pressure $${P_1}$$ to final pressure $$P{}_2.$$ The heat loss during the process is $$Q$$. The entropy changes $$\Delta S$$ of the gas is
A
$$mR\,\ln \left( {{{{P_2}} \over {{P_1}}}} \right)$$
B
$$mR\,\ln \left( {{{{P_1}} \over {{P_2}}}} \right)$$
C
$$mR\,\ln \left( {{{{P_2}} \over {{P_1}}}} \right) - {Q \over {{T_1}}}$$
D
zero
3
GATE ME 2011
MCQ (Single Correct Answer)
+2
-0.6
In an experimental set-up, air flows between two stations $$P$$ and $$Q$$ adiabatically. The direction of flow depends on the pressure and temperature conditions maintained at $$P$$ and $$Q$$. The conditions at station $$P$$ are $$150$$ $$kPa$$ and $$350$$ $$K.$$ The temperature at station $$Q$$ is $$300$$ $$K.$$ The following are the properties and relations pertaining to air:

Specific heat at constant pressure, $${C_p} = 1.005\,\,kJ/kg\,\,K;$$$Specific heat at constant volume, $${C_v} = 0.718\,\,kJ/kg\,\,K;$$$
Characteristic gas constant, $$R=0.287$$ $$kJ/kgK.$$
Enthalpy $$h = {C_p}T,$$
Internal energy, $$u = {C_v}T.$$

If the air has to flow from station $$P$$ to station $$Q,$$ the maximum possible value of pressure in $$kPa$$ at station $$Q$$ is close to

A
$$50$$
B
$$87$$
C
$$128$$
D
$$150$$
4
GATE ME 2011
MCQ (Single Correct Answer)
+2
-0.6
In an experimental set-up, air flows between two stations $$P$$ and $$Q$$ adiabatically. The direction of flow depends on the pressure and temperature conditions maintained at $$P$$ and $$Q$$. The conditions at station $$P$$ are $$150$$ $$kPa$$ and $$350$$ $$K.$$ The temperature at station $$Q$$ is $$300$$ $$K.$$ The following are the properties and relations pertaining to air:

Specific heat at constant pressure, $${C_p} = 1.005\,\,kJ/kg\,\,K;$$$Specific heat at constant volume, $${C_v} = 0.718\,\,kJ/kg\,\,K;$$$
Characteristic gas constant, $$R=0.287$$ $$kJ/kgK.$$
Enthalpy $$h = {C_p}T,$$
Internal energy, $$u = {C_v}T.$$

If the pressure at station $$Q$$ is $$50$$ $$kPa,$$ the change in entropy $$\left( {{S_Q} - {S_p}} \right)$$ in $$kJ/kgK$$ is

A
$$-0.155$$
B
$$0$$
C
$$0.160$$
D
$$0.355$$
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