scholarly journals Heat-transfer characteristics of ammonia-water falling film generation outside a vertical tube

2017 ◽  
Vol 21 (3) ◽  
pp. 1251-1259 ◽  
Author(s):  
Chao Luo ◽  
Jun Zhao ◽  
Weibin Ma
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Water Temperature ◽  
Water Solution ◽  
Hot Water ◽  
Falling Film ◽  
Ammonia Water ◽  
Overall Heat Transfer Coefficient ◽  
Spray Density

A heat transfer experimental of vertical out-tube falling film was conducted with different inlet spray density of ammonia-water solution and inlet hot water temperature. The inlet liquid mass concentration was selected as 60% of ammonia. The experiments showed that the overall heat transfer coefficient increases with the increase of inlet spray density and a maximum overall heat transfer coefficient could be obtained in an optimum spray density of ammonia-water solution, ?, between 0.26 and 0.29 kg/ms. The generation of ammonia vapor outside the vertical falling film had a similar trend with the overall heat transfer coefficient basing on different spray density. The effect of hot water temperature difference, ?T, on overall heat transfer coefficient showed that ?T between 10 and 13 K is the optimum temperature difference of the vertical falling film generation

Heat Transfer Coefficient in Falling Film Evaporators With Different Tube Arrangements

2012 ◽  
Author(s):  
Shengqiang Shen ◽  
Gangtao Liang ◽  
Yali Guo ◽  
Xingsen Mu ◽  
Rui Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Saturation Temperature ◽  
Horizontal Tube ◽  
Falling Film ◽  
Overall Heat Transfer Coefficient ◽  
Spray Density ◽  
Total Temperature

A set of experimental facilities were set up to measure overall heat transfer coefficient of horizontal-tube falling film evaporators with triangular, rotated square and square-pitch bundles. Effect of spray density, saturation temperature, total temperature difference and inlet steam velocity on the overall heat transfer coefficient K is studied respectively. The tubes are made of HAL77-2A aluminium brass with an outer diameter of 25.4 mm. Fluids inside and outside the tubes are steam and fresh water respectively. The results indicate that growth of spray density and saturation temperature helps to increase the K. The K could also be increased by reducing the total temperature difference. However, the impact of the inlet steam velocity on the K is less significant. The K in the evaporator with rotated square-pitch arrangement is supreme. Furthermore, space distribution of local overall heat transfer coefficient K̃ in the evaporators is also discussed. Based on this investigation, basic engineering design information will be provided to establish the governing parameters for horizontal-tube falling film evaporator in the field of seawater desalination.

scholarly journals Establishment of the falling film evaporation model and correlation of the overall heat transfer coefficient

2019 ◽  
Vol 6 (5) ◽  
pp. 190135 ◽  
Author(s):  
Jing Fang ◽  
Kaixuan Li ◽  
Mengyu Diao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Film Thickness ◽  
Liquid Film ◽  
Velocity Distribution ◽  
Transfer Coefficient ◽  
Falling Film ◽  
Overall Heat Transfer Coefficient ◽  
Proposed Model

In order to study the heat transfer of the falling film evaporator with phase change on both sides, in this paper we built the mathematical model and the physical model where the liquid film inside the tube is laminar and turbulent. The film thickness of the condensate at different axial positions, total condensate volume and velocity distribution, and temperature distribution of condensate outside the tube can be obtained by calculating the proposed model. Meanwhile, the liquid film thickness, velocity distribution and temperature distribution inside the tube were obtained by numerical simulation by considering the influence of the liquid film with different compositions on the heat transfer during fluid flow. With ethanol–water as the system, the overall heat transfer coefficient and heat transfer quantity of the falling film evaporator were obtained by the calculation of the model. The accuracy of the proposed model was confirmed by experiments. The model and the calculation of heat transfer proposed in this paper have enormous significance for the basic data and theoretical guidance of the heat transfer performance prediction and operational optimization of the evaporator.

Heat Exchanger Analysis Modified to Account for a Heat Source

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Vinod Narayanan ◽  
Murty Kanury ◽  
Jeromy Jenks
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Source ◽  
Transfer Coefficient ◽  
Source Term ◽  
Experimental Measurements ◽  
Ammonia Water ◽  
Overall Heat Transfer Coefficient

A modified heat exchanger analysis is developed here that accounts for a heat source, which is assumed to be volumetrically uniform in the hot fluid. The motivation for this work arises from the analysis of an ammonia-water absorber heat exchanger where a heat-of-absorption source term arises in the solution side. Utility of the analysis in deducing the overall heat transfer coefficient from experimental measurements is demonstrated.

scholarly journals Design, Fabrication and Performance Evaluation of a Shell and Tube Heat Exchanger for Practical Application

2020 ◽  
Vol 5 (8) ◽  
pp. 835-845
Author(s):  
Bashiru Abdulmumuni ◽  
Adedeji Mathew Ayoade ◽  
Ologunye Opeyemi Buhari ◽  
Azeez Rasheed Olatunde ◽  
Fanifosi Johnson Olaniyi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Cold Water ◽  
Hot Water ◽  
Feed Water ◽  
Capacity Ratio ◽  
Overall Heat Transfer Coefficient ◽  
Fouling Factor

A heat exchanger is a device used to transfer thermal energy between two or more fluids, at different temperatures in thermal contact. This paper focuses on a shell-and-tubes heat exchanger that involves two fluids (hot water and cold water) in contact with each other while the cold water flows through the tubes and hot water through the shell. Heat exchangers have special and practical applications in the feed water cooler in the process industries, power plants, chemical plants, refineries, process applications as well as refrigeration and air conditioning industry. The design calculations were carried out to determine the specifications of essential parameters for the development of the heat exchanger, data generated from the theoretical formulae were used to fabricate the heat exchanger using some locally available and durable materials, and the performance of the system was evaluated. Some of the parameters evaluated include heat duty, capacity ratio, effectiveness, overall heat transfer coefficient, and fouling factor. The heat exchanger was tested under various flow conditions and the results obtained were as follows; cold water inlet temperatures of (26, 26, 26, 27and 27) ºC increased to (59, 44, 39, 47 and 35) ºC after (10, 7½, 6½  8,  and 6) minutes and the hot water temperatures decreased from (100, 80, 75, 87 and 73) ºC to (73, 59, 55, 62 and 50) ºC, respectively. The design data and test data were compared in terms of the heat duty, capacity ratio, effectiveness, overall heat transfer coefficient, and fouling factor, the deviation is found to be 22.87%, 13.99%, 8.98%, 43.30%, and 43.30% respectively. The results obtained proved that the heat exchanger was effective, reliable and provides a good technical approach to evaluate the thermal performance of the heat exchanger and useful in conducting heat and mass transfer practical in thermodynamics laboratory.

scholarly journals A numerical model and validation of phase change material integrated thermoelectric radiant cooling panel

2019 ◽  
Vol 111 ◽  
pp. 01001
Author(s):  
Hansol Lim ◽  
Hye-Jin Cho ◽  
Seong-Yong Cheon ◽  
Soo-Jin Lee ◽  
Jae-Weon Jeong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Numerical Model ◽  
Surface Temperature ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Phase Change Material ◽  
Overall Heat Transfer Coefficient ◽  
Radiant Cooling ◽  
Change Material

A phase change material based radiant cooling panel with thermoelectric module (PCM-TERCP) is proposed in this study. It consists of two aluminium panels, and phase change materials (PCMs) sandwiched between the two panels. Thermoelectric modules (TEMs) are attached to one of the aluminium panels, and heat sinks are attached to the top side of TEMs. PCM-TERCP is a thermal energy storage concept equipment, in which TEMs freeze the PCM during the night whose melting temperature is 16○C. Therefore, the radiant cooling panel can maintain a surface temperature of 16◦C without the operation of TEM during the day. Furthermore, it is necessary to design the PCM-TERCP in a way that it can maintain the panel surface temperature during the targeted operating time. Therefore, the numerical model was developed using finite difference method to evaluate the thermal behaviour of PCM-TERCP. Experiments were also conducted to validate the performance of the developed model. Using the developed model, the possible operation time was investigated to determine the overall heat transfer coefficient required between radiant cooling panel and TEM. Consequently, the results showed that a overall heat transfer coefficient of 394 W/m2K is required to maintain the surface temperature between 16○C to 18○C for a 3 hours operation.

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