scholarly journals An Experimental Investigation of Water Vapor Condensation from Biofuel Flue Gas in a Model of Condenser, (2) Local Heat Transfer in a Calorimetric Tube with Water Injection

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1310
Author(s):  
Robertas Poškas ◽  
Arūnas Sirvydas ◽  
Vladislavas Kulkovas ◽  
Hussam Jouhara ◽  
Povilas Poškas ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flue Gas ◽  
Gas Flow ◽  
Water Injection ◽  
Middle Part ◽  
Total Heat ◽  
Gas Temperature ◽  
Total Heat Transfer ◽  
Condensing Heat Exchanger

In order for the operation of the condensing heat exchanger to be efficient, the flue gas temperature at the inlet to the heat exchanger should be reduced so that condensation can start from the very beginning of the exchanger. A possible way to reduce the flue gas temperature is the injection of water into the flue gas flow. Injected water additionally moistens the flue gas and increases its level of humidity. Therefore, more favorable conditions are created for condensation and heat transfer. The results presented in the second paper of the series on condensation heat transfer indicate that water injection into the flue gas flow drastically changes the distribution of temperatures along the heat exchanger and enhances local total heat transfer. The injected water causes an increase in the local total heat transfer by at least two times in comparison with the case when no water is injected. Different temperatures of injected water mainly have a major impact on the local total heat transfer until almost the middle of the model of the condensing heat exchanger. From the middle part until the end, the heat transfer is almost the same at different injected water temperatures.

scholarly journals An Experimental Investigation of Water Vapor Condensation from Biofuel Flue Gas in a Model of Condenser, (1) Base Case: Local Heat Transfer without Water Injection

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 844
Author(s):  
Robertas Poškas ◽  
Arūnas Sirvydas ◽  
Vladislavas Kulkovas ◽  
Povilas Poškas
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Flue Gas ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Water Injection ◽  
Vapor Condensation ◽  
Base Case ◽  
Water Vapor Condensation ◽  
Condensing Heat Exchanger

Waste heat recovery from flue gas based on water vapor condensation is an important issue as the waste heat recovery significantly increases the efficiency of the thermal power units. General principles for designing of this type of heat exchangers are known rather well; however, investigations of the local characteristics necessary for the optimization of those heat exchangers are very limited. Investigations of water vapor condensation from biofuel flue gas in the model of a vertical condensing heat exchanger were performed without and with water injection into a calorimetric tube. During the base-case investigations, no water was injected into the calorimetric tube. The results showed that the humidity and the temperature of inlet flue gas have a significant effect on the local and average heat transfer. For some regimes, the initial part of the condensing heat exchanger was not effective in terms of heat transfer because there the flue gas was cooled by convection until its temperature reached the dew point temperature. The results also showed that, at higher Reynolds numbers, there was an increase in the length of the convection prevailing region. After that region, a sudden increase was observed in heat transfer due to water vapor condensation.

Methods of Thermal Calculations for a Condensing Waste-Heat Exchanger

2014 ◽  
Vol 35 (4) ◽  
pp. 447-461 ◽  
Author(s):  
Paweł Rączka ◽  
Kazimierz Wójs
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Water Vapour ◽  
Flue Gas ◽  
Waste Heat ◽  
Pilot Scale ◽  
Dew Point ◽  
Steam Boiler ◽  
Heat Transfer Area ◽  
Condensing Heat Exchanger

Abstract The paper presents the algorithms for a flue gas/water waste-heat exchanger with and without condensation of water vapour contained in flue gas with experimental validation of theoretical results. The algorithms were used for calculations of the area of a heat exchanger using waste heat from a pulverised brown coal fired steam boiler operating in a power unit with a capacity of 900 MWe. In calculation of the condensing part, the calculation results obtained with two algorithms were compared (Colburn-Hobler and VDI algorithms). The VDI algorithm allowed to take into account the condensation of water vapour for flue gas temperatures above the temperature of the water dew point. Thanks to this, it was possible to calculate more accurately the required heat transfer area, which resulted in its reduction by 19 %. In addition, the influence of the mass transfer on the heat transfer area was taken into account, which contributed to a further reduction in the calculated size of the heat exchanger - in total by 28% as compared with the Colburn-Hobler algorithm. The presented VDI algorithm was used to design a 312 kW pilot-scale condensing heat exchanger installed in PGE Belchatow power plant. Obtained experimental results are in a good agreement with calculated values.

Analysis of Exhausting Flue Gas Temperature Abnormal Accompanied with the Boiler Load Changing

2013 ◽  
Vol 805-806 ◽  
pp. 1836-1842
Author(s):  
Qing Feng Zhang ◽  
Zhen Xin Wu ◽  
Zhen Ning Zhao
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Flue Gas ◽  
Gas Flow ◽  
Thermal Power ◽  
Transfer Principle ◽  
Air Leakage ◽  
Gas Temperature ◽  
Boiler Load ◽  
Hot Air

Based on the heat-transfer principle of air pre-heater, the influence mode of the changes of the air flow, the flue gas flow, the air leakage in different locations, to the temperature of the hot air and the exhausting gas was researched. The problem of a pulverized coal fired boiler, No.2, of a Thermal Power Plant, which the deviation of exhausting flue gas temperature increased to an abnormal extend when the boiler load rise up quickly was analyzed, the fault position and fault reason were located exactly, and the fault was eradicated by equipment maintenance at last. The results of this study have a certain significance to solve similar problems.

Reliable Method of a Non-Insulated Double-Pipe Heat Exchanger

2013 ◽  
Vol 284-287 ◽  
pp. 908-914
Author(s):  
King Leung Wong ◽  
Wen Lih Chen ◽  
Li Wen Po
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Total Heat ◽  
Heat Radiation ◽  
Total Heat Transfer ◽  
Double Pipe ◽  
Single Pipe ◽  
Pipe Heat

Log mean temperature difference (LMTD) method neglecting the influence of heat radiation is conventionally used to calculate the total heat transfer rate of heat exchangers. From recent investigation of a single-pipe heat exchanger in some practical situations, it is found that the total heat transfer rate error of single-pipe heat exchanger obtained by LMTD method is up to 40% in the situation of oxidized metal heat exchanger with higher surface emissivity located in ambient air with low heat convection coefficient. A log mean heat transfer rate (LMHTR) method considering heat radiation has been developed to calculate the total heat transfer rate of a single-pipe heat exchanger and more accurate results can be achieved. It is also found in the present investigation that LMTD method is also not suitable to apply to non-insulated double-pipe heat exchangers and a more accurate LMHTR method considering heat radiation is developed to obtain the more reasonable results.

One Method to Design a Heat Exchanger for Equipment Cooling Water

2017 ◽  
Author(s):  
Liao Yi ◽  
Chen Lei ◽  
Qiu Jinrong
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Water System ◽  
Cooling Water ◽  
Total Heat ◽  
Effective Length ◽  
Total Heat Transfer ◽  
Heat Exchanger Design ◽  
Design Result ◽  
Exchanger Tube

The equipment cooling water heat exchanger is an important device in the component cooling water system. In this paper, the Bell-Delaware method was applied to achieve a preliminary design of equipment cooling water heat exchanger and a very mature design software HTRI6.0 was used to check the results. On the basis of HTRI6.0 results, the relative error of the total heat transfer coefficient and the total heat transfer area were 1.35% and 0.2%, respectively. The effective length of the heat exchanger tube and the number of the baffle plates are consistent. The design result of the Bell-Delaware method meets the actual heat transfer requirements and the heat exchanger design satisfies the requirements of vibration.

scholarly journals Combined Heat Transfer Mechanisms in the Porous Char Layer Formed from the Intumescent Coatings under Fire

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 200
Author(s):  
Lingyun Zhang ◽  
Yupeng Hu ◽  
Minghai Li
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Thermal Conduction ◽  
Total Heat ◽  
Surface Radiation ◽  
Total Heat Transfer ◽  
Char Layer ◽  
Competition Result ◽  
Transfer Mechanisms ◽  
Combined Heat Transfer

This study examines the combined heat transfer by thermal conduction, natural convection and surface radiation in the porous char layer that is formed from the intumescent coating under fire. The results show that some factors, such as the Rayleigh number, conductivity ratio, emissivity, radiation–conduction number, void fraction and heating mode have a certain effect on the total heat transfer. In addition, the natural convection of the air in the cavity always inhibits surface radiation among the solid walls and thermal conduction, and the character of the total heat transfer is the competition result of the three heat transfer mechanisms.

The Energy-Saving Optimization of the Organic Heat Transfer Material Heater

2012 ◽  
Vol 455-456 ◽  
pp. 284-288
Author(s):  
Wei Li Gu ◽  
Jian Xiang Liu
Keyword(s):  
Heat Transfer ◽  
Energy Saving ◽  
Flue Gas ◽  
Theoretical Basis ◽  
Operation Management ◽  
Exergy Loss ◽  
Irreversible Processes ◽  
Design Parameters ◽  
Gas Temperature

this paper studies the typical irreversible processes such as combustion and heat transfer with temperature difference based on the theory of thermodynamics, analyzes the influencing factors on exergy loss in irreversible processes, on the basis of this analysis, proposes the energy-saving optimization measures on design and operation management of the organic heat transfer material heater, and specially points out that in the design process, objective function can be constructed with the exergy loss as evaluation index to determine the outlet flue gas temperature of furnace and the flue gas temperature, and provides theoretical basis for the determination of design parameters.

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