# Thermodynamics and Heat Engine Supply Exam July 2020

```Enrolment No:
UNIVERSITY OF PETROLEUM AND ENERGY STUDIES
Supplementary Examination, July 2020
Course: Thermodynamics and Heat Engine
Semester: III
Program: B.Tech ASE , ASE+AVE, B. Tech (Geo Informatics),
B.Tech Applied Petroleum + Sp Upstream,
B. Tech(Geo Science Engineering)
Time 03 hrs.
Course Code: GNEG241,MEPD2002,
Max. Marks: 100
Instructions:
1. Read the Instruction carefully before attempting
2. For Theory based : Type the Answers in word file
3. For Figures if any : Draw a free hand sketch and insert the same word file
4. For Numerical : Solve it in a paper and insert in the same word file
5. Upload as a single word file for all the Question in Blackboard.
will be considered for evaluation only through Blackboard. No other mode of submission is acceptable.
SECTION A [60 Marks]
S. No.
Q1
Marks
Since its introduction in 1903 by Aegidius Elling of Norway, steam injection between the
combustion chamber and the turbine is used even in some modern gas turbines currently in
operation to cool the combustion gases to a metallurgical-safe temperature while increasing the
mass flow rate through the turbine. Currently there are several gasturbine power plants that use
steam injection to augment power and improve thermal efficiency. Consider a gas-turbine power
plant whose pressure ratio is 8. The isentropic efficiencies of the compressor and the turbine are
80 percent, and there is a regenerator with an effectiveness of 70 percent. When the mass flow
rate of air through the compressor is 40 kg/s, the turbine inlet temperature becomes 1700 K. But
the turbine inlet temperature is limited to 1500 K, and thus steam injection into the combustion
gases is being considered. However, to avoid the complexities associated with steam injection,
it is proposed to use excess air (that is, to take in much more air than needed for complete
combustion) to lower the combustion and thus turbine inlet temperature while increasing the
mass flow rate and thus power output of the turbine. Evaluate this proposal, and compare the
thermodynamic performance of “high air flow” to that of a “steam-injection” gas-turbine power
plant under the following design conditions: the ambient air is at 100 kPa and 25&deg;C, adequate
NOTE : The submission time of the Question Paper Answer Sheet is 24 Hhrs from the scheduled time
(exceptional provision due to extraordinary circumstance due to COVID-19 and due to internet connectivity issues in the farflung areas).
No Submission will be entertained after 24 Hrs
20
water supply is available at 20&deg;C, and the amount of fuel supplied to the combustion chamber
remains constant
Q2
Q3
Nitrogen gas is compressed from 80 kPa and 27 0C to 480 kPa by a 10-kW compressor.
Determine the mass flow rate of nitrogen through the compressor, assuming the compression
process to be (a) isentropic, (b) polytropic with n = 1.3, (c) isothermal, and (d) ideal two-stage
polytropic with n = 1.3.
An ideal Rankine steam cycle modified with two closed feedwater heaters and one open
feedwater heater is shown below. The power cycle receives 100 kg/s of steam at the high pressure
inlet to the turbine. The feedwater heater exit states for the boiler feedwater and the condensed
steam are the normally assumed ideal states. Use the data provided in the tables given below to
(a) Sketch the T-s diagram for the ideal cycle.
(b) Determine the fraction of mass y extracted for the open feedwater heater.
(c) If, in addition to your result from part (b), the fraction of mass entering the high pressure
turbine at state 7 extracted for the closed feedwater heater operating at 140 kPa is z 5 0.0655,
and at 1910 kPa the extraction fraction is w 5 0.0830, determine the cooling water temperature
rise in the condenser, in 8C, when the cooling water flow rate is 4200 kg/s. Assume cp 5
4.18kJ/kg&middot;K for cooling water.
(d) Determine the rate of heat rejected in the condenser and the thermal efficiency of the plant.
15
25
NOTE : The submission time of the Question Paper Answer Sheet is 24 Hhrs from the scheduled time
(exceptional provision due to extraordinary circumstance due to COVID-19 and due to internet connectivity issues in the farflung areas).
No Submission will be entertained after 24 Hrs
SECTION B [40 Marks]
Q4
Consider a building whose annual air-conditioning load is estimated to be 40,000 kWh in an
area where the unit cost of electricity is Rupees 0.10/kWh. Two air conditioners are considered
for the building. Air conditioner A has a seasonal average COP of 2.3 and costs Rupees 5500 to
purchase and install. Air conditioner B has a seasonal average COP of 3.6 and costs Rupees
7000 to purchase and install. All else being equal, determine which air conditioner is a better
10
Q5
Q6
Water is being heated in a vertical piston–cylinder device. The piston has a mass of 40 kg and a
cross-sectional area of 150 cm2. If the local atmospheric pressure is 100 kPa, determine the
temperature at which the water starts boiling
Justify the use of condenser in Rankine cycle. What happened if incase condenser not working.
5
5
Q7
A heat pump operates on a Carnot heat pump cycle with a COP of 8.7. It keeps a space at 24&deg;C
by consuming 2.15 kW of power. Determine the temperature of the reservoir from which the
heat is absorbed and the heating load provided by the heat pump.
5
Q8
Explain perpetual motion machine of first and second kind.
5
Q9
Derive the equation of efficiency for Diesel cycle through P-V and T- S plot.
5
Q 10
Discuss the concept of available energy and maximum useful work.
5
NOTE : The submission time of the Question Paper Answer Sheet is 24 Hhrs from the scheduled time
(exceptional provision due to extraordinary circumstance due to COVID-19 and due to internet connectivity issues in the farflung areas).
No Submission will be entertained after 24 Hrs
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