Chapter 3 FIRST PHASE DEVELOPMENTS
3.2 EXPERIMENTAL PROCEDURE
In India, Bureau of Indian Standards sets guidelines for testing the thermal efficiencies for all types of cooking stoves. For LPG cooking stoves, the thermal ef
according to Indian Standards (IS)
thermal efficiencies of cooking stoves in the present work were estimated by conducting the water boiling test and the procedure followed is
Insulated mixing tube of a conventional burner filled with metal balls as porous media
Two sections of porous burner with different combinations Zone 1
3 mm diameter Metal balls
Metal balls of diameter 8 mm 3 - 4 mm average
diameter pebbles
Metal balls of diameter 8 mm Ball with insulation and 3 - 4 mm average
Diameter pebbles
Metal balls of diameter 8 mm Pebble and metal chips insulation with
the reduced height between the burner bottom surface of the
3 - 4 mm average diameter
Metal chips
EXPERIMENTAL PROCEDURE
In India, Bureau of Indian Standards sets guidelines for testing the thermal efficiencies for all types of cooking stoves. For LPG cooking stoves, the thermal efficiencies are determined according to Indian Standards (IS) 4246:2002. Following the guidelines of IS 4246:2002, thermal efficiencies of cooking stoves in the present work were estimated by conducting the water boiling test and the procedure followed is briefly described.
Insulated mixing tube of a conventional burner filled with metal
of CZ and PZ Zone 2 Metal balls of diameter 8 mm Metal balls of diameter 8 mm Metal balls of diameter 8 mm Metal chips
In India, Bureau of Indian Standards sets guidelines for testing the thermal efficiencies for all ficiencies are determined Following the guidelines of IS 4246:2002, thermal efficiencies of cooking stoves in the present work were estimated by conducting the
A 5 kg LPG cylinder was connected to a regulator and then with a pressure gauge in between to the burner. To purge air and to establish the required gas pressure, LPG at a pressure of 30 mbar was allowed to pass through the burner for a few minutes. Only one burner of the cooking stove was tested at a time. The diameter and height of the aluminum pan used for water boiling test was selected according to the range of gas flow rate used in the experiment.
The pan mass along with its lid and the mass of water used in the pan was noted. The weighing balance used has a resolution of 1 gm (make: Sartorious) Temperature T1 of water was noted and recorded as long as it remained constant. The cylinder was disconnected and its weight m1 was noted and then again the cylinder was connected to the line. The gas supply was turned on and it was ignited. Water was heated up to 80oC and for uniformity in temperature; stirring was started and continued until the end of the test when the temperature T2 of water reached 90 ± 1°C. Then the burner was put off. The cylinder was disconnected and its new weight m2 was noted. The difference in the weight, m2 - m1 (= mf) estimates the mass of gas used to heat water from T1 to T2. The weighing balance used has a resolution of 0.1 g (make: TULA, India).
The percentage of thermal efficiency,
η
th, of the stove was calculated based on the following formula:ߟ௧ = (݉ௐ × ܥௐ + ݉ × ܥ)(ܶଶ− ܶଵ)
݉ × ܥܸ (3. 1)
where, mW is the mass of water, Cw and Cp are specific heat capacity of water and aluminium pan respectively, mp is the mass of pan along with the lid and stirrer and mf is the mass of the fuel. The calorific value of the fuel, CV = 45636.12 kJ/kg, specific heat of water and aluminium are Cp = 0.8959 kJ/kg-K andCW = 4.1826 kJ/kg-K, respectively. For every burner,
experiments were repeated at least three times and average of the three values was taken as the final efficiency. The same procedure was also followed when porous media was used.
The uncertainty analysis was carried out by considering the inaccuracies in the mass and temperature measurements. A maximum value of uncertainty in the thermal efficiency calculation was found to be ± 2.8%. The detailed uncertainty analysis is presented in Appendix- III. To compare the thermal efficiencies and emissions of the burners with porous media with those of the conventional LPG cooking stoves, a market survey was carried out to get the various types of burners used in conventional domestic cooking stoves. Seven types of burners were selected from the Indian market. Burner heads of the same are shown in Fig.
3.1. The thermal efficiencies of the seven types of conventional burners selected from the Indian market were in the range 60 - 65%. The typical measured efficiency curve of a conventional domestic cooking burner is shown in Fig. 3.3. The burners shown in Fig. 3.1 follow the same trends, i.e. thermal efficiency found to decrease with increase in wattage (increases heat loss to the surroundings) as shown in Fig. 3.3.
Fig. 3.3 Typical efficiency graph of the conventional domestic cooking burner
The flue gas sampling was done according to the IS: 4246. A hood shown in the below Fig.
3.4 was fabricated according to the dimensions mentioned in the IS: 4246. The hood was placed above the burner along with the vessel and the portable flue gas analyser probe was place in the first sampling hole. The main purpose of the hood is to isolate the flue gases from the atmospheric air to avoid any influence on the former by the later. A portable flue gas analyser is used (TESTO 350XL, maker: TESTO, Germany) for recording CO and NOx emissions. The detailed specifications of the instrumentation/equipments used in the experiments are given in Appendix - IV.
a. Hood for flue gas sampling b. Schematic of the hoof for flues gas sampling (imported from IS: 4246)
Fig. 3.4 Photo and schematic of the hood for flues gas sampling Sampling
hole
The typical CO and NOx emission levels of the domestic cooking burner in the range of equivalence ratio 0.9-1.0 are illustrated in Fig. 3.5. Both the CO and NOx emissions rise with the power and the maximum values observed were around 1050 mg/m3 and 216 mg/m3, respectively, which are much higher than the recommended values [Kandpal et al., 2002] of World Health Organisation (WHO).
Fig. 3.5 Typical emissions graph for a conventional domestic cooking stove