JEPPIAAR ENGINEERING COLLEGE
CHENNAI
DEPARTMENT OF MECHANICAL ENGINEERING
113301 – ENGINEERING THERMODYNAMICS
UNIT – 1 : ASSIGNMENT QUESTIONS

1. A piston and cylinder machine contains a fluid system which passes through a complete cycle of four processes. During a cycle, the sum of all heat transfers is -170kJ. The system completes 100 cycles per min. Complete the following table showing the method for each item, and compute the net rate of work output in kW.

2. Air at 1.02 bar, 22ᵒC, initially occupying a cylinder volume of 0.015 m3 is compressed reversibly and adiabatically by a piston to a pressure of 6.8 bar. Calculate : (i) the final temperature, (ii) the final volume & (iii) the work done. (Ans: T2=507.25 K, V2= 0.003869, W=24.513kJ)

3. Air at 30ᵒC and 1 bar is compressed reversibly and polytropically from 5m3 to 1m3 . Calculate the final temperature, pressure and also the work done and heat transfer if the index of compression is 1, 1.4 and 0.9 respectively. Assume Cp=1.005kJ/kgK and Cv=0.7178 kJ/kgK.

4. 2m3 of H2 at a pressure of 1 bar and 20ᵒC is compressed isentropically to 4 bar. The same gas is expanded isothermally restored to o9riginal volume by constant volume heat rejection...

...czyET 3200 – EngineeringThermodynamics
Homework Assignment #6
Due June 15, 2013 @ 5:00 PM
Problem 4.8 - A Home Heat Pump for Space Heating
We wish to do a preliminary thermodynamic evaluation of a 1kW input power home heat pump system for space heating using refrigerant R134a. Consider the following system flow diagram
Thus the heat pump system absorbs heat from the evaporator placed outside in order to pump heat into the air flowing through the insulated duct over the condenser section. The fan provides an air flow of 8 m3/minute, which is enough to cool the refrigerant in the condenser to 30°C, In this analysis we will neglect the power provided to the fan. We also assume that the duct is adiabatic, and that all the heat rejected by the condenser is absorbed by the air flowing in the duct.
Plot the four processes on the P-h diagram provided below and use the R134a refrigerant property tables in order to determine the following:
* Determine the mass flow rate of the refrigerant R134a [0.0185kg/s]
* Determine the mass flow rate of the air flowing in the insulated duct [0.161kg/s].
* Determine the heat rejected by the condenser [-3.7kW]. Assuming that all this heat is absorbed by the air, determine the exit temperature of the air at station (6) [37.9°C]. Is this value reasonable? Why? (Note: This problem involves heat being transferred from the refrigerant in the condenser to the air flowing through the...

...First Law-Exercise:
Problem 1: A volume 10 m3 contains 8 kg of oxygen at a temperature of 300 K. Find the work necessary to decrease the volume to 5 m3, (a) at a constant pressure and (b) at constant temperature. (c) What is the temperature at the end of the process in (a)? (d) What is the pressure at the end of process in (b)? (e) Show both processes in the p-V plane. Problem 2: The temperature of an ideal gas at an initial pressure p1 and volume V1 is increased at constant volume until the pressure is doubled. The gas is then expanded isothermally until the pressure drops to its original value, where it is compressed at constant pressure until the volume returns to its initial value. (a) Sketch these processes in the p-V plane and in the p-T plane. (b) Compute the work in each process and the net work done in the cycle if n = 2 kmoles, p1 = 2 atm and V1 = 4 m3. Problem 3: A 735 W stirring motor is applied to a tank of water. The tank contains 25 kg of water, and the stirring action is applied for 1 hour. Assuming that the tank is perfectly insulated, calculate the change in internal energy of the water. Also calculate the rise in temperature of the water, assuming that the process occurs at constant volume and that cv for water may be taken as 4.18 kJ/kg.K. Problem 4: A 0.0283 m3 container is filled with air at 1.365 bar and 37.77oC. Calculate the final pressure in the container if 10544.82 J of heat are added. Assume ideal gas behaviour, with constant specific heats....

...Thermodynamics Lab
Introduction:
Thermodynamics is the study of energy which can exist in many forms, such as heat, light, chemical energy, and electrical energy. The variables that thermodynamics can be used to define include temperature, internal energy, entropy, and pressure. Temperature, relating to thermodynamics, is the measure of kinetic energy in the particles of a substance. Light is usually linked to absorbance and emission in thermodynamics while pressure, linked with volume, can do work on an entire system. The entropy is the measure of the flow of heat through a system whose equation is for a thermodynamically reversible process as
Regarding thermodynamics, there are three laws the first of which is appropriately named the First Law of Thermodynamics. The First Law of Thermodynamics states that energy can be changed from one form to another, but it cannot be created or destroyed. The total amount of energy and matter in the Universe must remains constant at all times, however it can change from one form to another. In other words energy is always conserved with the amount remaining constant. The Second Law of Thermodynamics states that in...

...Chapter 6
Introduction to thermodynamics
Topics First law of thermodynamics. Deﬁnitions of internal energy and work done, leading to dU = dq + dw. Heat capacities, Cp = CV + R. Reversible and irreversible processes. Various types of expansion, isothermal, adiabatic. CV and Cp according to kinetic theory, monatomic gases, other gases. The meaning of temperature, empirical temperature scale, perfect gas scale, the second law of thermodynamics,thermodynamic temperature scale. So far, we have concentrated upon developing a microscopic model for the behaviour of gases. We now turn our attention to the macroscopic description of solids, liquids and gases, which is concerned with the bulk properties of properties of substances. This is the subject of thermodynamics and, in contrast to our analysis so far, we deny that the various forms of matter are actually composed of atoms and molecules. Thermodynamics is a large and very powerful branch of physics. In this chapter, we show how thermodynamics can provide crucial clues about the physics of our microscopic model.
6.1 First Law of Thermodynamics
The ﬁrst law of thermodynamics is a statement about the conservation of energy.
1
Statistical and Quantum Physics Energy is conserved when heat is taken into account.
2
This is a somewhat more subtle statement than might appear at ﬁrst sight....

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APPLICATION OF THERMODYNAMICSTHERMODYNAMIC OF GASES
(ADIABATIC CHANGE)
In thermodynamic of gases, we can study about the changes to the internal energy of gas and factors affecting the internal energy. Thermodynamic also involves work done and heat supplied or lost by a gas.
THERMODYNAMICS
The study of temperature, heat, and related macroscopic properties comprises the branch of physics.Thermodynamics deals with processes which cause energy changes (internal energy) as a result of heat flow to or from a system and/or of work done on or by a system.
Internal energy, U is the sum of the kinetic energy and potential energies of the molecules of the system.
Internal energy, U = Kinetic Energy + Potential Energy of molecules
Work done by a gas when a gas expands. Conversely, work done is on a gas when a gas is compressed.
W =
= p ∆V
= Pressure x Increase in volume
Thermodynamic Equilibrium
We define this type of equilibrium by saying that when two system are placed together until no further change occurs in any macroscopic property, then two have reached thermodynamic equilibrium in each other.
TWO SYSTEM HAVE THE SAME TEMPERATURE IF THEY ARE IN THERMODYNAMIC EQUILIBRIUM.
First Law of Thermodynamics
The first law of thermodynamics is based on the principle...

...COMSATS – LANCASTER
(Dual Degree Program)
EEE-112 Engineering Mechanics and Thermodynamics
Assignment # 1 Submission date: Mon, Sep 17, 2012
1. A certain fluid at 10 bar is contained in a cylinder behind a piston, the initial volume being 0.05 m3. Calculate the work done by the fluid when it expands reversibly:
a. at constant pressure to a final volume of 0.2 m3;
b. according to a linear law to a final volume of 0.2 m3 and a final pressure of 2 bar;
c. according to a law Pv = constant to a final volume of 0.1 m3;
d. according to a law Pv3 = constant to a final volume of 0.06 m3;
e. according to a law, P = (A/v2) – (B/v), to a final volume of 0.1 m3 and a final pressure of 1 bar, where A and B are constants.
f. Sketch all processes on a Pv diagram.
2. 1 kg of a fluid expands reversibly according to a linear law from 4.2 bar to 1.4 bar; the initial and final volumes are 0.004 m3 and 0.02 m3. The fluid is then cooled reversibly at constant pressure, and finally compressed reversibly according to a law Pv = constant back to the initial conditions of 4.2 bar and 0.004 m3. Calculate the work done in each process and the net work of the cycle. Sketch the cycle on a Pv diagram.
3. A fluid at 0.7 bar occupying 0.09 m3 is compressed reversibly to a pressure of 3.5 bar according to a law Pvn = constant. The fluid is then heated reversibly at constant volume until the pressure is 4 bar; the...

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saturated vapor enters the turbine. The condenser pressure is
6 kPa. Determine
(a) the thermal efficiency.
(b) the back work ratio.
(c) the net work of the cycle per unit mass of water flowing,
in kJ/kg.
(d) the heat transfer from the working fluid passing through
the condenser, in kJ per kg of steam flowing.
(e) Compare the results of parts (a)–(d) with those of Problem
8.6, respectively, and comment.
8.8 Plot each of the quantities calculated in Problem 8.6 versus
turbine inlet temperature ranging from the saturation temperature
at 18 MPa to 560C. Discuss.
8.9 A power plant based on the Rankine cycle is under
development to provide a net power output of 10 MW. Solar
collectors are to be used to generate Refrigerant 22 vapor at
1.6 MPa, 50C, for expansion through the turbine. Cooling
water is available at 20C. Specify the preliminary design of
the cycle and estimate the thermal efficiency and the refrigerant
and cooling water flow rates, in kg/h.
8.10 Refrigerant 134a is the working fluid in a solar power plant
operating on a Rankine cycle. Saturated vapor at 60C enters
the...

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THERMODYNAMICS - THEORY
A control volume may involve one or more forms of work at the same time. If the boundary of the control volume is stationary, the moving boundary work is zero, and the work terms involved are shaft work and electric work. Another work form with the fluid is flow work.
Flow Work (Flow Energy)
A Flow Element
Flow Work with Imaginary Piston
Click to View Movie (68 kB)
Work is needed to push the fluid into or out of the boundaries of a control volume if mass flow is involved. This work is called the flow work (flow energy). Flow work is necessary for maintaining a continuous flow through a control volume.
Consider a fluid element of volume V, pressure P, and cross-sectional area A as shown left. The flow immediately upstream will force this fluid element to enter the control volume, and it can be regarded as an imaginary piston. The force applied on the fluid element by the imaginary piston is:
F = PA
The work done due to pushing the entire fluid element across the boundary into the control volume is
Wflow = FL = PAL = PV
For unit mass,
wflow = Pv
The work done due to pushing the fluid element out of the control volume is the same as the work needed to push the fluid element into the control volume.
Total Energy of a Flowing Fluid
Total Energy of a Flowing Fluid
Click to View Movie (52 kB)
The total energy of a simple compressible...