Heat Transfer Design in Adsorption Refrigeration Systems for Efficient Use of Low Grade Thermal Energy

2010 ◽  
Author(s):  
R. Z. Wang ◽  
Z. Z. Xia ◽  
L. W. Wang ◽  
Z. S. Lu ◽  
S. L. Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Thermal Energy ◽  
High Performance ◽  
Low Grade ◽  
Adsorption Refrigeration ◽  
High Efficient ◽  
Sorption Systems

Adsorption refrigeration and heat pump systems have been considered as very important means for the efficient use of low grade thermal energy in the temperature range of 60–150°C. Sorption systems are merely heat exchanger based thermodynamic systems, and therefore a good design to optimize heat and mass transfer with reaction or sorption processes is very important for high performance of the systems. Studies on heat and mass transfer enhancement in adsorption beds have been done extensively. Notable techniques is whereby the adsorbent bed is fitted with finned heat exchanger embedded with adsorbent particles, or the adsorbent particles may be compressed and solidified and then coupled with finned tube or plate heat exchangers. The use of expanded graphite seems to be an effective method to improve both heat and mass transfer in the reaction bed. Studies have also shows the need to enhance the heat transfer in adsorption bed to match with the heat transfer of thermal fluids. Use of heat pipes and good thermal loop design could yield higher thermal performances of a sorption system, when coupled with adsorption beds to provide heating and cooling to the beds. A novel design with passive evaporation, known as rising film evaporation coupled with a gravity heat pipe was introduced for high cooling output. It has also been shown that heat and mass recovery in the internal sorption systems is critical, and novel arrangement of thermal fluid and refrigerant may result in high performance sorption systems. Based upon the above researches, various sorption systems have been developed, and high efficient performances have been reached. Typical sorption systems include (1) A silica gel-water adsorption water chillier with a COP about 0.55 when powered with 80°C hot water, (2) A CaCl2-ammonia adsorption refrigerator with a COP over 0.3 at −20 °C when powered with 120 °C water vapor, which has a specific cooling power about 600 W/kg-adsorbent. The above mentioned systems have shown that solid sorption systems have become market potential products, and low grade thermal energy, which is usually considered as waste heat, could be utilized to provide high grade cooling. This paper gives details of high efficient solid sorption systems recently developed, their heat transfer design, thermodynamic system coupling, and performance test results. Some examples of low grade thermal powered cooling systems are also presented.

CFD-based structure optimization of plate bundle in plate-fin heat exchanger considering flow and heat transfer performance

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yao Li ◽  
Haiqing Si ◽  
Jingxuan Qiu ◽  
Yingying Shen ◽  
Peihong Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Field Performance ◽  
High Specific Surface Area ◽  
Calculation Model ◽  
Air Separation ◽  
Transfer Efficiency ◽  
Heat Transfer Efficiency

Abstract The plate-fin heat exchanger has been widely applied in the field of air separation and aerospace due to its high specific surface area of heat transfer. However, the low heat transfer efficiency of its plate bundles has also attracted more attention. It is of great significance to optimize the structure of plate-fin heat exchanger to improve its heat transfer efficiency. The plate bundle was studied by combining numerical simulation with experiment. Firstly, according to the heat and mass transfer theory, the plate bundle calculation model of plate-fin heat exchanger was established, and the accuracy of the UDF (User-Defined Functions) for describing the mass and heat transfer was verified. Then, the influences of fin structure parameters on the heat and mass transfer characteristics of channel were discussed, including the height, spacing, thickness and length of fins. Finally the influence of various factors on the flow field performance under different flow states was integrated to complete the optimal design of the plate bundle.

Review of Technology Used to Improve Heat and Mass Transfer Characteristics of Adsorption Refrigeration System

2016 ◽  
Vol 24 (02) ◽  
pp. 1630003 ◽  
Author(s):  
Anirban Sur ◽  
Randip K. Das
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Waste Heat ◽  
Transfer Characteristic ◽  
Low Grade ◽  
Transfer Performance ◽  
Refrigeration System ◽  
Adsorption Refrigeration ◽  
System A ◽  
Absorption Refrigeration System

Researchers proved that, heat powered adsorption refrigeration technology is very effective methods for reutilization of low-grade thermal energy such as industrial waste heat, solar energy, and exhaust gases from engines. But to make it commercially competitive with the well-known vapor compression and absorption refrigeration system, the processes require high rates of heat and mass transfer characteristic between adsorbate and adsorbent as well as externally supplied heat exchanging fluid. This paper reviews various techniques that have been developed and applied to enhance the heat transfer and mass transfer in adsorber beds, and also discuss their effects of the performance on adsorption system. A comprehensive literature review has been conducted and it was concluded that this technology, although attractive, has limitations regarding its heat and mass transfer performance that seem difficult to overcome. Therefore, more researches are required to improve heat and mass transfer performance and sustainability of basic adsorption cycles.

A Fully Wet and Fully Dry Tiny Circular Fin Method for Heat and Mass Transfer Characteristics for Plain Fin-and-Tube Heat Exchangers Under Dehumidifying Conditions

2006 ◽  
Vol 129 (9) ◽  
pp. 1256-1267 ◽  
Author(s):  
Worachest Pirompugd ◽  
Chi-Chuan Wang ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Heat Exchangers ◽  
Heat Transfer Characteristic ◽  
Transfer Characteristic ◽  
Tube Heat Exchanger ◽  
Mass Transfer Characteristic ◽  
Transfer Characteristics

This study proposes a new method, namely the “fully wet and fully dry tiny circular fin method,” for analyzing the heat and mass transfer characteristics of plain fin-and-tube heat exchangers under dehumidifying conditions. The present method is developed from the tube-by-tube method proposed in the previous study by the same authors. The analysis of the fin-and-tube heat exchangers is carried out by dividing the heat exchanger into many tiny segments. A tiny segment will be assumed with fully wet or fully dry conditions. This method is capable of handling the plain fin-and-tube heat exchanger under fully wet and partially wet conditions. The heat and mass transfer characteristics are presented in dimensionless terms. The ratio of the heat transfer characteristic to mass transfer characteristic is also studied. Based on the reduced results, it is found that the heat transfer and mass transfer characteristics are insensitive to changes in fin spacing. The influence of the inlet relative humidity on the heat transfer characteristic is rather small. For one and two row configurations, a considerable increase of the mass transfer characteristic is encountered when partially wet conditions take place. The heat transfer characteristic is about the same in fully wet and partially wet conditions provided that the number of tube rows is equal to or greater than four. Correlations are proposed to describe the heat and mass characteristics for the present plain fin configuration.

Heat transfer design in adsorption refrigeration systems for efficient use of low-grade thermal energy

Energy ◽  
2011 ◽  
Vol 36 (9) ◽  
pp. 5425-5439 ◽  
Author(s):  
R.Z. Wang ◽  
Z.Z. Xia ◽  
L.W. Wang ◽  
Z.S. Lu ◽  
S.L. Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Energy ◽  
Low Grade ◽  
Adsorption Refrigeration

Overall Efficiency of a Radial Fin Assembly Under Dehumidifying Conditions

1998 ◽  
Vol 120 (4) ◽  
pp. 299-304 ◽  
Author(s):  
L. Rosario ◽  
M. M. Rahman
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Relative Humidity ◽  
Heat And Mass Transfer ◽  
Heat Transfer Rate ◽  
Transfer Process ◽  
Transfer Rate ◽  
Total Heat ◽  
Overall Efficiency

The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing the heat transfer rate with and without fins under the same operating conditions. Calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. An analysis of the overall efficiency for the assembly was also done. Results were compared to those under dry conditions, wherever appropriate. Comparison between present results and those published for rectangular as well as radial fins under fully wet conditions were made. These comparisons established the validity of the present model. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature. The fin efficiency decreased with relative humidity.

Hydrodynamics and Heat Transfer of Liquid Nitrogen Laminar Falling Films in Cryogenic Heat Exchanger

2009 ◽  
Author(s):  
Ying-Bai Xie ◽  
Cheng Zhao ◽  
Jian-Cheng Tang ◽  
Ying-Cheng Mai
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Liquid Nitrogen ◽  
Thin Liquid Film ◽  
Convection Heat Transfer ◽  
Theoretical Models ◽  
Transfer Method ◽  
The Impact

As an efficiency heat and mass transfer method, thin liquid film has been widely used in industry. This paper studies on liquid nitrogen laminar film flows in the brazed cryogenic heat exchanger with 2.3mm distance between plates. Simplified theoretical models are established based on the characteristics of both the dynamic and heat and mass transfer of nitrogen film. Relationship between the dimensionless thickness and the coefficient of heat convection of liquid nitrogen film is derived. And the impact of rate of vapor content, intensity of interfacial convection heat transfer and Reynolds numbers are calculated and analyzed.

Heat and mass transfer characteristics of organic sorbent coated on heat transfer surface of a heat exchanger

2008 ◽  
Vol 44 (11) ◽  
pp. 1305-1313 ◽  
Author(s):  
Hideo Inaba ◽  
Fujio Komatsu ◽  
Akihiko Horibe ◽  
Naoto Haruki ◽  
Akito Machida
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Heat Transfer Surface ◽  
Transfer Characteristics

Design and Testing of High-Performance Mini-Channel Graphite Heat Exchangers in Thermoelectric Energy Recovery Systems

2017 ◽  
Author(s):  
Terry J. Hendricks ◽  
Bryan Mcenerney ◽  
Fivos Drymiotis ◽  
Ben Furst ◽  
Abhibit Shevade
Keyword(s):  
Heat Transfer ◽  
Thermal Expansion ◽  
High Temperature ◽  
Heat Exchanger ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Energy Recovery ◽  
High Performance ◽  
Thermoelectric Energy ◽  
Graphite Heat

Recent national energy usage studies by Lawrence Livermore National Laboratory in 2015 [1] show that there is approximately 59 Quads (1015 Btu’s) of waste thermal energy throughout various industrial, residential, power generation, and transportation sectors of the U.S. economy. Thermoelectric energy recovery is one important technology for recovering this waste thermal energy in high-temperature industrial, transportation and military energy systems. Thermoelectric generator (TEG) systems in these applications require high performance hot-side and cold-side heat exchangers to provide the critical temperature differential and transfer the required thermal energy. High performance hot-side heat exchangers in these systems are often metal-based due to requirements for high-temperature operation, strength at temperature, corrosion resistance, and chemical stability. However, the generally selected metal-based hot-side heat exchangers (i.e., Inconels, Stainless Steels) suffer from low thermal conductivity, high thermal expansion, and high density, which degrades their thermal performance, leads to high thermal-expansion-driven stresses, and creates relatively high mass/high volume (i.e., low power density) TEG systems that are then difficult to fabricate and integrate into viable energy recovery systems. This paper describes the design and testing of a new, high-temperature minichannel graphite heat exchanger designed for operation up to 500°C that is a critical element of a high-power-density TEG power system for aircraft energy recovery. This high-performance graphite heat exchanger represents a new state-of-the-art standard in high-temperature heat exchangers for TEG systems, which provides higher thermal transport, less thermal expansion at operation, lower system level stresses on TE components, and a lighter weight TEG system. This new heat exchanger creates a new design paradigm in TEG system design for terrestrial energy recovery and potential NASA technology infusion into terrestrial energy system applications. This paper will present and discuss the key heat transfer, pressure drop, pumping power analyses and design tradeoffs that created this unique design. Heat transfer and pressure drop modeling was performed with both empirical models based on known heat transfer and friction factor correlations and COMSOL thermal/fluid dynamic modeling of the graphite heat exchanger structure. We will also discuss resulting thermal transport and heat fluxes predicted at the TEG interface level. Heat exchanger performance testing was performed under simulated operating conditions and correlation with test data at the anticipated operating temperature conditions will be presented and discussed.

Sign in / Sign up

Export Citation Format

Share Document