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GUJARAT TECHNOLOGICAL UNIVERSITY
DIPLOMA ENGINEERING – SEMESTER – VI• EXAMINATION – SUMMER 2016
Subject Code: 3361907 Date: 23/05/2016
Subject Name: Thermal systems and Energy Efficiency
Time: 10:30 AM to 01:00 PM 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.
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Q.1 Answer any seven out of ten. 14
1. Why energy conservation is required?
2. Write Renewable and non - renewable energy sources.
3. State the function of the furnace.
4. List some common types of heat exchangers.
5. Define thermal efficiency of the air compressor.
6. Define refrigeration and Air conditioning.
7. Write boiler specifications.
8. What is T.E.T.D.?
9. Define the term overall heat transfer co-efficient.
10. Define Free Air Delivery (F.A.D) for the air compressor and write its units.
Q.2 (a) What is sankey diagram? What is important of sankey diagram? 03
OR
(a) Draw the sankey diagram for air compressor system. 03
(b) List the method are used for calculation of boiler efficiency. 03
OR
(b) List the various losses in boiler. 03
(c) State the steps required foe energy conservation in furnaces. 04
OR
(c) List the various furnaces and explain any one 04
(d) What is fouling factor? What is the reason for it? 04
OR
(d) Explain the NTU method for the heat exchanger. 04
Q.3 (a) Explain thermodynamic type steam trap with sketch. 03
OR
(a) Explain the energy conservation act 2001. 03
(b) Using given data of furnace heat balance sheet draw sankey diagram using suitable scale considering gross fuel input as 100 % --- (i) useful output 44 % (ii) flue gas loss 38% (iii) wall loss 12% (iv) cooling loss 10% (v) stored heat 6 % 03
OR
(b) Explain L.M.T.D .method for parallel flow in heat exchanger. 03
(c) Describe leakage assessment method for air compressor with equation. 04
OR
(c) List various sensible and latent heat load for refrigeration system. 04
(d) Write the steps for improving boiler efficiency. 04
OR
(d) Explain infiltration and ventilation for air conditioning system. 04
Q.4 (a) Explain the principle of Co-Generation System based on gas turbine with diagram. 03
OR
(a) List the opportunities for energy saving in refrigeration and air conditioning system. 03
(b) One Plant has one compressor of capacity 1200 m3/h. Free air delivery of the compressor is carried out by filling the receiver. The test data are as follows: Receiver capacity : 10 m3Interconnecting pipe : 1 m3 Initial pressure in receiver : 1.0 kg/cm2Inlet air pressure to compressor 1.0 kg/cm2(a) Final pressure : 10kg/cm2Time taken to fill the receiver : 3 minutes (180 seconds) Power consumption during loading : 120 kW. Using these data find out 1. Free air delivery in m3/h 2. Specific power consumption in m3/h/ kW. 04
OR
(b) One restaurant with capacity of 300 people is to be air conditioned. Outside air condition is 35 ᵒC dry bulb temperatures and 50 % relative humidity. Inside air condition is 24 ᵒC dry bulb temperatures with 55% relative humidity. Ventilation requirement per person is 0.30 m3/person. Find out sensible heat load and latent heat load for this restaurant using psychometric chart. 04
(c) 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. 5 ton of oil is cooling from 200°C to 80°C and water is heating from 30°C to 90 °C Find out corrected L.M.T.D. for the heat exchanger using for counter flow and parallel flow and water flow rate. Specific heat of oil is 0.5 kcal /kg. 07
Q.5 (a) Calculate Free air delivery in m3/h and isothermal efficiency for air compressor using following data. Nozzle flow coefficient = 0.98 Nozzle diameter : 0.010 m Receiver Pressure 3.0 kg / cm2Inlet Pressure 1.00 kg / cm2(a) Inlet air temperature 34°C Pressure before nozzle 1.04 kg / cm2. Temperature before the nozzle 40°C Pressure difference across the nozzle = 0.035 kg / cm2 .Gas constant: 287 Joules / kg K. 04
(b) 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 : 80 % , H2 : 10.0 % , S : 3.0 %, O2 : 1.0 % GCV of oil = 10500 kCal/kg ; Percentage of oxygen in flue gas = 8 % ; Flue gas temperature = 230 ᵒC ; Ambient temperature = 29 ᵒC ; Humidity of air = 0.020 kg/kg of dry air ; Cp of flue gas = 0.23 kcal/kg ᵒC ; Cp of steam = 0.45 kcal/kg ᵒC. 04
(c) . Explain heat recovery system for furnace. 03
(d)An oil-fired reheating furnace has an operating temperature around 1500
C. Air fuel ratio is 15:1. Average O2 percentage in flue gas = 10 %. Cp of flue gas = 0.24 kcal/kg ᵒC. Flue gas temperature is 650 ૦C, Ambient temperature = 35 ૦C, GCV of oil = 10300 kCal/kg. Using these data find out percentage heat loss in flue gas. 03
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