• Journal of ILASS-Korea
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• v.26 no.2
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• pp.96-103
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• 2021

In order to improve the overall efficiency and meet the emission regulations of boiler systems, the heat exchanging methods between inlet air and exhaust gas have been used in boiler systems, named as the waste-heat-recovery condensing boiler. Recently, to further improve the overall efficiency and to reduce the NOx emission simultaneously, the concept of the water injection into the inlet air is introduced. This study suggests the models for the optimized design parameters of water injection for waste-heat-recovery condensing boilers and performs the analysis regarding the water injection amount and droplet sizes for the optimized water injection. At first, the required amount of the water injection was estimated based on the 1^st law of thermodynamics under the assumption of complete evaporation of the injected water. The result showed that the higher the inlet air and exhaust gas temperature into the heat exchanger, the larger the amount of injected water is needed. Then two droplet evaporation models were proposed to analyze the required droplet size of water injection for full evaporation of injected water: one is the evaporation model of droplet in the inlet air and the other is that on the wall of heat exchanger. Based on the results of two models, the maximum allowable droplet sizes of water injection were estimated in various boiler operating conditions with respect to the residence time of the inlet air in the heat exchanger.

• New & Renewable Energy
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• v.9 no.4
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• pp.32-39
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• 2013

A 2-loop waste heat recovery system with Rankine steam cycles for the improvement of fuel efficiency of gasoline vehicles has been investigated. A high temperature loop is used to recover waste heat from exhaust gas and a low temperature loop is used to recover waste heat from cold engine coolant. This paper has dealt with a layout of low temperature loop system, the review of the velocity contours through numerical analysis. According to the result of analysis, the designed heat exchanger. And comparing with flow analysis results, LT Boiler is safe to operation.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.639-647
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• 2014

Due to global warming and depletion of fossil fuels, technologies reducing $CO_2$ emission and increasing fuel efficiency simultaneously are required. An exhaust gas heat recovery system is a technology to satisfy both issues. This study analyses three types of heat exchanger installed on an exhaust pipe. In case of plate type heat exchanger, back pressure rapidly increased and maximum cylinder pressure reduced in high speed and maximum load, and back pressure increased over twice and specific fuel consumption also increased up to 2% which were the highest increasing rate. In case of fin tube type, the amounts of exhaust emissions and specific fuel consumption rate were less than the other two types. The effect of shell and tube was in the middle. Making a decision by only the effect on engine performance, a fin tube type is the best for exhaust heat recovery systems.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.79-84
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• 2011

Air pollutants from a small marine diesel engine are increasing and the IMO(International Marine Organization) regulation asked for its reduction. In this study, NOx reduction technologies such as improvement of various cooling systems are applied to the small marine diesel engine. The various cooling systems are a intercooler, a heat exchanger for engine coolant, and an exhaust manifold by water cooling. These systems are tested on an engine dynamometer and a exhaust gas analyzer by a marine diesel engine test regulation. Test results are shows that the small marine engine are satisfied the IMO NOx regulations; Tire II.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.8
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• pp.690-696
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• 2003

This paper presents the heat recovery performance of water fluidized-bed heat exchanger. Temperature and humidity ratio of waste gas are considered as important parameters in this study. Therefore, the heat recovery rate through water fluidized-bed heat exchanger for exhaust gases with various temperatures and humidity ratios can be estimated from the results of this study. Mass flow ratio (the ratio of mass flow rate of water to that of gas) and temperature of inlet water are also considered as important operating variables. Increase of heat recovery rate can be obtained through either high mass flow ratio or low temperature of inlet water with resultant low recovered temperature. The heat recovery performance with the mass flow ratio of about up to 10 has been investigated. The effect of number of stages of water fluidized-bed on the heat recovery performance has been also examined in this study.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3053-3058
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• 2008

We develop a heat exchanger modules for a multi-burner boiler. The heat exchanger module is kind of a heat recovery steam generator (HRSG). This heat recovery system has 4 heat exchanger modules. The 1st module consists of 27 bare tubes due to high temperature exhaust gas and the others consist of 27 finned tubes. The maximum steam pressure of each module is 1 MPa and tested steam pressure is 0.7 MPa. In order to test these heat exchanger modules, we make a 0.5t/h flue tube boiler (LNG, $40\;Nm^3/h$). We tested the heat exchanger module with changing the position of each heat exchanger module. We measured the inlet and outlet temperature of each heat exchanger module and calculated the heat exchange rate. The results show that if module C is placed at second stage (the 1st stage is always module O, bare tube module), there is no need to attach an additional heat exchanger module. In this case the exit temperature of module C is low enough to enter an economizer which is more effective in heat recovery than a heat exchanger module.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.345-350
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• 2008

The present study has been conducted to develop a heat recovery system for a 1 MW class gas engine based cogeneration system. In the cogeneration system, heat is recovered from two parts, which are jacket water and exhaust gas. The heat from the jacket water is recovered by a plate type heat exchanger and used for the room heating and/or hot water supply. The heat from the exhaust gas is used to generate steam. For both of the heat recovery devices, 1/5 scaled tests are performed and the data are compared to the conventional correlations for the design.

• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.124-124
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• 2004

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.4
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• pp.248-257
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• 2010

An exhausted heat recovery system for a small gas engine cogeneration plant was investigated. The system was designed and built in a 300 kW class cogeneration demonstrative system. The basic performance was tested depending on load variation, and installed to a field site as a bottoming heat and power supply system. The exhaust gas heat exchangers (EGHXs) in shell-and-tube type and shell-and-plate type were tested. The entire efficiency of the cogeneration system was estimated between 85 to 90% under the 100% load condition, of which trend appears higher in summer due to the less thermal loss than in winter. Power generation efficiency and thermal efficiency was measured in a range of 31~33% and 54~57%, respectively.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1025-1030
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• 2008

We develop heat exchanger modules for a multi-burner boiler. The heat exchanger module is kind of a heat recovery steam generator (HRSG). This heat recovery system has 4 heat exchanger modules. The 1st module consists of 27 bare tubes due to high temperature exhaust gas and the others consist of 27 finned tubes. The maximum steam pressure of each module is 10 bar and tested steam pressure is 4 bar. In order to test these heat exchanger modules, we make a 0.5t/h flue tube boiler (LNG, $40\;Nm^3/h$). The test results of 100% boiler load show that heat transfer rate of 1st module is 49.7 Mcal/h which is 34% of total heat transfer rate and that of 2nd module is 82.6 Mcal/h which is 57% of total heat transfer rate. The reason of higher the heat transfer rate of 2nd module than that of 1st module is that the 2nd heat exchanger module has finned tubes instead of bare tube. The boiler load 50% results show that only 2 heat exchanger modules are needed to extract the heat from the flue gas to water. From this result, it is very important of optimum design of the first finned tube among all water tubes.