This research is to study in heat transfer of hot water tank from an air conditioner which is a cylinder type and has a hot water pipe around the tank. It is used for finding a position and a pattern of distribution of the hot water pipe around the tank in the highest heat transfer condition. The study uses the cylinder of hot water tank filled 45 liters of 25 oC water. An experiment separates in 3 positions of pipe wrapping which are the bottom the center and the top of the tank. Then 80 oC of hot water run thought the hot water pipe which is wrapped around the tank for 120 minutes. The result of the experiment shows that tubing position that causes the highest heat transfer is at the bottom of tank. Pipe wrapping at the bottom of the tank has the heat transfer higher than the top of the tank at 30%. Furthermore this experiment studies in spacing of hot water pipe. There are 3 types for testing which are spacing hot water pipe as one time two times and three times of diameter of pipe. The result illustrates that spacing the hot water pipe can significantly increase the heat transfer. The heat transfer of spacing the hot water pipe in three times of diameter of pipe is higher 5.8 % than spacing in one times. In addition this research is to study in the effect of turbulent flow on the heat transfer by installing agitator in order to stir water in the tank. The result is that water stirring in the tank for increasing the heat transfer is not effective for investment because the energy using for stirring is higher than the enhanced heat transfer

This research aims to develop the waste heat energy conversion device to generate electricity through a thermoelectric generator (TEG) which is called “CHEU. This device is applied to the LPG cookstove that serves as a waste heat source. The thermoelectric generator with 4 modules in series connection is used to convert heat energy to electricity. The present research shows a modification of the CHEU based on two concepts as follows: (1) re-design the structure for heat transfer improvement and (2) select the high capability of TEG to support a high temperature from a heat source as a result of (1). In this study the modified CHEU is called “MCHEU”. A heat-load condition is set as the gas pressure of LPG which varies in a range of 0.1 - 0.6 kg/cm2 and the throttle valve is fixed approximately at 40% of a fully opened throttle while the air entrainment is fully opened throttle. Also the water-cooling system is used for heat dissipation. Base on the performance evaluation of MCHEU the interesting results are drawn as follows: 1) the maximum temperature difference is on an average value of 278.5oC at a maximum heat load condition while a maximum voltage current and power are on an average value of 18.83 V 5.67 A and 107 W respectively. 2) The temperature difference of MCHEU is higher than that of CHEU with an average value of 50%. 3) The output power obtained by MCHEU is higher than that of CHEU with an average value of 52% and takes less time about 40% for fully charging a battery (12V 7.5Ah). Nevertheless MCHEU usage does not affect the thermal efficiency of a cookstove. 4) The efficiency of an energy conversion obtained by MCHEU is 20% which is higher than that of CHEU about 2%.

The objectives of this study is to increase efficiency of steam boiler 2.5 ton per hour which used liquid petroleum gas LPG as fuel. bringing heat recovery inside boiler chimney stack to preheat feed water with technology heat Exchanger Economize. Taking the economizer with its pipe length of 1000 mm and 62 mm diameter for 64 pipe is a cross flow with staggered tube to increase water temperature before entering the boiler pass to deaerator The study is carried out to compare the differences and savings of the feed water temperature steam boiler efficiency and fuel consumption between having the economizer installed and uninstalled. reference to study The result after installed the heat exchanger economizer the feed water is passed into steam boiler deaerator higher temperature from 38.30°C to 67.20°C which leads to increase efficiency of steam boiler from 81.59 % to 85.65 % meaning that the fuel consumption of steam boiler will be reduced 4.97 %