scholarly journals Mathematical simulation of the flue-gas recovery system for coal-fired boilers based on the direct-contact heat exchanger

2017 ◽  
Vol 205 ◽  
pp. 321-328 ◽  
Author(s):  
Jingyi Wang ◽  
Lin Fu ◽  
Xiling Zhao ◽  
Jinzi Zhao
Keyword(s):  
Heat Exchanger ◽  
Mathematical Simulation ◽  
Flue Gas ◽  
Direct Contact ◽  
Contact Heat ◽  
Gas Recovery ◽  
Recovery System ◽  
Direct Contact Heat Exchanger

Experimental Study of Natural Gas Combustion Flue Gas Waste Heat Recovery System Based on Direct Contact Heat Transfer and Absorption Heat Pump

2013 ◽  
Author(s):  
Xian Zhou ◽  
Hua Liu ◽  
Lin Fu ◽  
Shigang Zhang
Keyword(s):  
Heat Exchanger ◽  
Flue Gas ◽  
Direct Contact ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Contact Heat ◽  
Absorption Heat Pump ◽  
Return Water ◽  
Recovery System

Condensing boiler for flue gas waste heat recovery is widely used in industries. In order to gain a portion of the sensible heat and latent heat of the vapor in the flue gas, the flue gas is cooled by return water of district heating through a condensation heat exchanger which is located at the end of flue. At low ambient air temperature, some boilers utilize the air pre-heater, which makes air be heated before entering the boiler, and also recovers part of the waste heat of flue gas. However, there are some disadvantages for these technologies. For the former one, the low temperature of the return water is required while the utilization of flue gas heat for the latter one is very limited. A new flue gas condensing heat recovery system is developed, in which direct contact heat exchanger and absorption heat pump are integrated with the gas boiler to recover condensing heat, even the temperature of the return water is so low that the latent heat of vapor in the flue gas could not be recovered directly by the general condensing technologies. Direct contact condensation occurs when vapor in the flue gas contacts and condenses on cold liquid directly. Due to the absence of a solid boundary between the phases, transport processes at the phase interface are much more efficient and quite different from condensation phenomena on a solid surface. Additionally, the surface heat exchanger tends to be more bulky and expensive. In this study, an experimental platform of the new system is built, and a variety of experimental conditions are carried out. Through the analysis of the experimental data and operational state, the total thermal efficiency of the platform will be increased 3.9%, and the system is reliable enough to be popularized.

scholarly journals Modelling of Technological Solutions to 4th Generation DH Systems

2017 ◽  
Vol 20 (1) ◽  
pp. 5-23 ◽  
Author(s):  
Edgars Vigants ◽  
Toms Prodanuks ◽  
Girts Vigants ◽  
Ivars Veidenbergs ◽  
Dagnija Blumberga
Keyword(s):  
Mass Transfer ◽  
Heat Exchanger ◽  
Flue Gas ◽  
Direct Contact ◽  
Positive Impact ◽  
District Heating ◽  
Heating Equipment ◽  
Contact Heat ◽  
Wet Gas ◽  
Direct Contact Heat Exchanger

Abstract Flue gas evaporation and condensing processes are investigated in a direct contact heat exchanger - condensing unit, which is installed after a furnace. By using equations describing processes of heat and mass transfer, as well as correlation coherences for determining wet gas parameters, a model is formed to create a no-filling, direct contact heat exchanger. Results of heating equipment modelling and experimental research on the gas condensing unit show, that the capacity of the heat exchanger increases, when return temperature of the district heating network decreases. In order to explain these alterations in capacity, the character of the changes in water vapour partial pressure, in the propelling force of mass transfer, in gas and water temperatures and in the determining parameters of heat transfer are used in this article. The positive impact on the direct contact heat exchanger by the decreased district heating (DH) network return temperature shows that introduction of the 4th generation DH system increases the energy efficiency of the heat exchanger. In order to make an assessment, the methodology suggested in the paper can be used in each particular situation.

New metrics for measuring multiphase mixing effects in a direct-contact heat exchanger

2019 ◽  
Vol 147 ◽  
pp. 592-601 ◽  
Author(s):  
Jianxin Xu ◽  
Qingtai Xiao ◽  
Zhihan Lv ◽  
Junwei Huang ◽  
Ruoxiu Xiao ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Direct Contact ◽  
Contact Heat ◽  
Mixing Effects ◽  
Direct Contact Heat Exchanger

scholarly journals Analytical Modelling of a Spray Column Three-Phase Direct Contact Heat Exchanger

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Hameed B. Mahood ◽  
Adel O. Sharif ◽  
Seyed Ali Hosseini ◽  
Rex B. Thorpe
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Direct Contact ◽  
Relative Velocity ◽  
Contact Heat ◽  
Spray Column ◽  
Three Phase ◽  
Direct Contact Heat Exchanger

An analytical model for the temperature distribution of a spray column, three-phase direct contact heat exchanger is developed. So far there were only numerical models available for this process; however to understand the dynamic behaviour of these systems, characteristic models are required. In this work, using cell model configuration and irrotational potential flow approximation characteristic models has been developed for the relative velocity and the drag coefficient of the evaporation swarm of drops in an immiscible liquid, using a convective heat transfer coefficient of those drops included the drop interaction effect, which derived by authors already. Moreover, one-dimensional energy equation was formulated involving the direct contact heat transfer coefficient, the holdup ratio, the drop radius, the relative velocity, and the physical phases properties. In addition, time-dependent drops sizes were taken into account as a function of vaporization ratio inside the drops, while a constant holdup ratio along the column was assumed. Furthermore, the model correlated well against experimental data.

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