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GUJARAT TECHNOLOGICAL UNIVERSITY
DIPLOMA ENGINEERING – SEMESTER – I • EXAMINATION – SUMMER 2015
Subject Code: 3361907 Date:14-05-2015
Subject Name: Thermal Systems and Energy Efficiency
Time: 10:30am to 1:30pm Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make Suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of programmable & Communication aids are strictly prohibited.
5. Use of only simple calculator is permitted in Mathematics.
6. English version is authentic.
7. Standard data sheet (given with GTU syllabus) is allowed in examination.
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Q.1 Answer any seven out of ten. 14
1. Define Primary and Secondary energy sources with example.
2. State the function of steam trap.
3. Define High grade and low grade energy source with example.
4. State the function of the furnace and write its main types.
5. List some common applications of heat exchangers.
6. List different parameters necessary to measure boiler efficiency for Indirect method.
7. Define Free Air Delivery for the air compressor and write its units.
8. List the characteristics of an efficient furnace.
9. Define refrigeration and Air conditioning.
10. List the instruments used to measure various parameters of refrigeration and air conditioning system.
Q.2 (a) Explain energy conservation Act-2001 in brief. 03
OR
(a) State the importance of energy conservation. 03
(b) Classify furnaces in detail. 03
OR
(b) Explain general concept of furnace with sketch. 03
(c) Explain in brief about opportunities for energy saving in steam distribution system. 04
OR
(c) Explain inverted bucket type steam trap with sketch. 04
(d) Explain energy saving measures for furnaces in context of following parameter. (i) excess air (ii) Heat distribution (iii) furnace pressure. 04
OR
(d) Using given data of furnace heat balance sheet draw sankey diagram using suitable scale considering gross fuel input as 100 % --- (i) useful output 40 % (ii) flue gas loss 35% (iii) wall loss 10% (iv) cooling loss 10% (v) stored heat 5 % 04
Q.3 (a) Describe pump up method for capacity assessment of air compressor with equation. 03
OR
(a) Describe leakage assessment method for air compressor with equation. 03
(b) Explain in brief about pull down effect and storage temperature effect of refrigeration. 03
OR
(b) State types of sensible heat load and latent heat load for refrigeration. 03
(c) Explain for heat exchanger (i) fouling factor (ii) LMTD correction factor. 04
OR
(c) Classify heat exchanger and state the characteristics of an efficient heat exchanger. 04
(d) One Plant has one compressor of capacity 1680 m3/h. Free air delivery of the compressor is carried out by filling the receiver. The test data are as follows:
Receiver capacity : 10 m3
Interconnecting pipe : 1 m3
Initial pressure in receiver : 1.0 kg/cm2
Inlet air pressure to compressor 1.0 kg/cm2 (a)
Final pressure : 8.25 kg/cm2
Time taken to fill the receiver : 3 minutes (180 seconds)
Power consumption during loading : 150 kW
Using these data find out free air delivery in m3/h and specific power
consumption in m3/h/ kW. 04
OR
(d) Calculate Free air delivery in m3/h for air compressor using following data.
Nozzle flow coefficient = 0.98
Nozzle diameter : 0.08 m
Receiver Pressure – 3.5 kg / cm2
Inlet Pressure – 1.04 kg / cm2 (a)
Inlet air temperature 30°C
Pressure before nozzle – 1.08 kg / cm2
Temperature before the nozzle 40°C
Pressure difference across the nozzle = 0.036 kg / cm2
Gas constant : 287 Joules / kg K 04
Q.4 (a) Explain infiltration and ventilation for air conditioning system. 03
OR
(a) List any five energy saving opportunities for refrigeration system. 03
(b) Explain in brief about radiation and convection recuperators, employed in furnaces with sketch. 04
OR
(b) Why do furnaces operate at low efficiency? Write the range of approximatepercentage of efficiency achieved in furnaces. Also discuss the methods by which furnace efficiency can be improved in brief. 04
(c) The following are the data collected for an oil fired package boiler. Find out the efficiency of the boiler by indirect method.Ultimate analysis of oil : C : 84 % , H2 : 13.0 % , S : 3.0 %, O2 : 1.0 %GCV of oil = 11000 kCal/kg ; Percentage of oxygen in flue gas = 7 % ; Flue gas temperature = 250 ᵒC ; Ambient temperature = 27 ᵒC ; Humidity of air = 0.02 kg/kg of dry air ; Cp of flue gas = 0.23 kcal/kg ᵒC ; Cp of steam = 0.45 kcal/kg ᵒC. 07
Q.5 (a) One restaurant with capacity of 200 people is to be air conditioned. Outside air condition is 36 ᵒC dry bulb temperature and 50 % relative humidity. Inside air condition is 20 ᵒC dry bulb temperature with 60% relative humidity. Ventilation requirement per person is 0.25 m3. Find out sensible heat load and latent heat load for this restaurant using psychrometric chart. 04
(b) A shell and tube heat exchanger of following configuration is considered being used for oil cooler with oil at the shell side and water at the tube side:Tube side dimensions: 460 nos X 25.4 mm, OD X 2.11 mm thick X 7211 mm long with 2 pass. Find out corrected LMTD for the heat exchanger. The monitored parameters for counter flow arrangement as below:
Parameters Units Inlet Outlet
Hot fluid flow kg/h 720000 720000
Cold fluid flow kg/h 890000 890000
Hot fluid temp ᵒC 145 102
Cold fluid temp ᵒC 25.5 49 04
(c) An oil-fired reheating furnace has an operating temperature around 1250 ᵒC. Air fuel ratio is 14:1. Average O2 percentage in flue gas = 12 %. Cp of flue gas = 0.24 kcal/kg ᵒC. Flue gas temperature is 750 ᵒC, Ambient temperature = 40 ᵒC, GCV of oil = 10000 kCal/kg. Using these data find out percentage heat loss in flue gas. 03
(d) Explain the principle of Co-Generation System based on steam turbine with diagram. 03
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