# Question 2.47: A source S1 can supply heat energy at the rate of 200 kJ/s a...

A source $S_1$ can supply heat energy at the rate of 200 kJ/s at 320° C and source $S_2$ can supply 2000 kJ/s at 75° C. Which source would you choose to supply energy to an ideal reversible heat engine if the temperature of surroundings is 35° C ?

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Question: 2.54

## 1 kg of ice at – 5°C is exposed to the atmosphere which is at 27°C. The ice melts and comes into thermal equilibrium. Determine the entropy increase of the universe. For ice, cp = 2.093 kJ/kg. °C. Latent heat of fusion of ice = 333.33 kJ/kg. ...

The system is shown in Fig 2.59. \begin{ali...
Question: 2.53

## A heat pump working on a reserved carnot cycle takes in energy from a reservoir at 5°C and delivers it to another reservoir where temperature is 77°C. The heat pump derives power for its operation from a reversible engine operating within the higher and lower temperature 1077°C and 77°C. For 100 ...

The system is shown in Fig 2.58. \begin{ali...
Question: 2.52

## Two identical bodies of constant heat capacity are at the same initial temperature Ti . A refrigerator operates between these two bodies until one body is cooled to temperature T2 . If the bodies remain at constant pressure and undergo no change of phase, show that the minimum amount of work needed ...

Let $\quad T_i$= initial temperature ...
Question: 2.51

## A vessel of capacity 3 m³ contains air at a pressure of 2 bar and temperature 300 K. Additional air is pumped into the system until the pressure rises to 30 bar and temperature to 330 K. Determine (a) the mass of air pumped (b) heat transferred, and (c) the change in entropy if the air is cooled ...

(a) \begin{aligned}&m_1=\frac{p_1 V_1}{...
Question: 2.50

## An insulated vessel containing air has two compartments separated by a conducting diaphram. Compartment A is of capacity 0.030 m³ at 2 bar and 300K. Compartment B is of capacity 0.025 m³ at 4.5 bar and 450 K. Find (a) equilibrium temperature, and (b) change in entropy of the system. Take Cν = ...

m_A=\frac{p_1 V_1}{R T_1}=\frac{2 \times 10...
Question: 2.49

## 2700 kJ/min at 800° C is supplied to an engine which rejects at 125° C. If heat rejected is (a) 1000 kJ/min, (b) 800 kJ/min, and (c) 1200 kJ/min, specify the process. ...

\begin{aligned}&T_1=800+273=1073 \mathr...
Question: 2.48

## An engine working on Carnot cycle absorbs Q1 units of heat from a source at T1 and rejects Q2 units of heat to a sink at T2 . The temperature of the working fluid is θ1 and θ2 , where θ1 T2. If θ1 = T1 – kQ1 and θ2 = T2 + kQ2 where k is constant, then show that efficiency of the ...

\eta=1-\frac{Q_2}{Q_1}=1-\frac{\theta_2}{\t...
Question: 2.46

## A reversible engine with 45% thermal efficiency discharges 1600 kJ/min at 30°C to a pond. Find the temperature of the source which supplies heat to the engine and power developed by the engine. ...

\begin{aligned}T_2 &=30+273=303 \ K \\Q...
Question: 2.45

## In a Carnot cycle the lowest pressure and temperature are equal to 1 bar and 20°C and isothermal compression pressure is 4 bar. Pressure after isentropic compression is 10 bar and after isothermal heat addition process is 5 bar. Calculate (a) the highest temperature in the cycle, (b) the change in ...

The cycle is shown in Fig 2.56 \begin{align...
\begin{aligned}&T_1=1000+273=1273 \ K \...