Energy Efficient Polymers for Gas-Liquid Heat Exchangers

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Patrick Luckow ◽  
Avram Bar-Cohen ◽  
Peter Rodgers ◽  
Juan Cevallos
Keyword(s):  
Thermal Conductivity ◽  
Life Cycle ◽  
Heat Exchanger ◽  
Natural Gas ◽  
Energy Expenditure ◽  
Heat Exchangers ◽  
Sea Water ◽  
Coefficient Of Performance ◽  
Offshore Platforms ◽  
Compression Process

The compression process necessary for the liquefaction of natural gas on offshore platforms generates large amounts of heat, usually dissipated via sea water cooled plate heat exchangers. To date, the corrosive nature of sea water has mandated the use of metals, such as titanium, as heat exchanger materials, which are costly in terms of life cycle energy expenditure. This study investigates the potential of a commercially available, thermally conductive polymer material, filled with carbon fibers to enhance thermal conductivity by an order of magnitude or more. The thermofluid characteristics of a prototype polymer seawater-methane heat exchanger that could be used in the liquefaction of natural gas on offshore platforms are evaluated based on the total coefficient of performance (COPT), which incorporates the energy required to manufacture a heat exchanger along with the pumping power expended over the lifetime of the heat exchanger, and compared with those of conventional heat exchangers made of metallic materials. The heat exchanger fabricated from a low energy, low thermal conductivity polymer is found to perform as well as, or better than, exchangers fabricated from conventional materials, over its full lifecycle. The analysis suggests that a COPT nearly double that of aluminum, and more than ten times that of titanium, could be achieved. Of the total lifetime energy use, 70% occurs in manufacturing for a thermally enhanced polymer heat exchanger compared with 97% and 85% for titanium and aluminum heat exchangers, respectively. The study demonstrates the potential of thermally enhanced polymer heat exchangers over conventional ones in terms of thermal performance and life cycle energy expenditure.

Energy Efficient Polymers for Gas-Liquid Heat Exchangers

2008 ◽  
Author(s):  
Patrick Luckow ◽  
Avram Bar-Cohen ◽  
Peter Rodgers ◽  
Juan Cevallos
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Conductive Polymer ◽  
Coefficient Of Performance ◽  
Offshore Platforms ◽  
Compression Process ◽  
Cooling Fluid ◽  
Thermally Conductive ◽  
Liquid Heat ◽  
Better Than

The present study explores the thermofluid characteristics of a seawater-methane heat exchanger that could be used in the liquefaction of natural gas on offshore platforms. The compression process generates large amounts of heat, usually dissipated via plate heat exchangers using seawater as a convenient cooling fluid. Such an application mandates the use of a corrosion resistant material. Metals such as titanium, expensive in terms of both energy and currency, are a common choice. The “total coefficient of performance,” or COPT, which incorporates the energy required to manufacture a heat exchanger along with the pumping power expended over the lifetime of the heat exchanger, is used to compare conventional metallic materials to thermally conductive polymers. The results reveal that heat exchangers fabricated of low energy, low thermal conductivity polymers can perform as well as, or better than, those fabricated of conventional materials, over the full lifecycle of the heat exchanger. Analysis of a prototypical seawater-methane heat exchanger, built from a thermally conductive polymer, suggests that a COPT nearly double that of aluminum, and more than ten times that of titanium, could be achieved.

Binary Particle Mixtures as a Heat Transfer Media in Shell-and-Plate Moving Packed Bed Heat Exchangers

2021 ◽  
Author(s):  
Chase Ellsworth Christen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Packed Bed ◽  
Particle Sizes ◽  
Overall Heat Transfer Coefficient ◽  
Solid Media

Solid particles are being considered in several high temperature thermal energy storage systems and as heat transfer media in concentrated solar power (CSP) plants. The downside of such an approach is the low overall heat transfer coefficients in shell-and-plate moving packed bed heat exchangers caused by the inherently low packed bed thermal conductivity values of the low-cost solid media. Choosing the right particle size distribution of currently available solid media can make a substantial difference in packed bed thermal conductivity, and thus, a substantial difference in the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers. Current research exclusively focuses on continuous unimodal distributions of alumina particles. The drawback of this approach is that larger particle sizes require wider particle channels to meet flowability requirements. As a result, only small particle sizes with low packed bed thermal conductivities have been considered for the use in the falling-particle Gen3 CSP concepts. Here, binary particle mixtures, which are defined in this thesis as a mixture of two continuous unimodal particle distributions leading to a continuous bimodal particle distribution, are considered to increase packed bed thermal conductivity, decrease packed bed porosity, and improve moving packed bed heat exchanger performance. This is the first study related to CSP solid particle heat transfer that has considered the packed bed thermal conductivity and moving packed bed heat exchanger performance of bimodal particle size distributions at room and elevated temperatures. Considering binary particle mixtures that meet particle sifting segregation criteria, the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers can be increased by 23% when compared to a monodisperse particle system. This work demonstrates that binary particle mixtures should be seriously considered to improve shell-and-plate moving packed bed heat exchangers.

scholarly journals Method of Averaging the Effective Thermal Conductivity Based on Thermal Response Tests of Borehole Heat Exchangers

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3737
Author(s):  
Aneta Sapińska-Śliwa ◽  
Tomasz Sliwa ◽  
Kazimierz Twardowski ◽  
Krzysztof Szymski ◽  
Andrzej Gonet ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Effective Thermal Conductivity ◽  
Heat Exchangers ◽  
Thermal Response ◽  
Method Of Averaging ◽  
Thermal Response Test ◽  
Borehole Heat Exchanger ◽  
Measurement Results ◽  
Borehole Heat Exchangers

This work concerns borehole heat exchangers and their testing using apparatus for thermal response tests. In the theoretical part of the article, an equation was derived from the known equation of heat flow, on which the interpretation of the thermal response test was based. The practical part presents the results of several measurements taken in the AGH Laboratory of Geoenergetics. They were aimed at examining the potential heat exchange capacity between the heat carrier and rock mass. Measurement results in the form of graphs are shown in relation to the examined, briefly described wells. Result analysis made it possible to draw conclusions regarding the interpretation of the thermal response test. The method of averaging the measurement results was subjected to further study. The measuring apparatus recorded data at a frequency of one second, however such accuracy was too large to be analyzed efficiently. Therefore, an average of every 1 min, every 10 min, and every 60 min was proposed. The conclusions stemming from the differences in the values of effective thermal conductivity in the borehole heat exchanger, resulting from different data averaging, were described. In the case of three borehole heat exchangers, ground properties were identical. The effective thermal conductivity λeff was shown to depend on various borehole heat exchanger (BHE) designs, heat carrier flow geometry, and grout parameters. It is important to consider the position of the pipes relative to each other. As shown in the charts, the best (the highest) effective thermal conductivity λeff occurred in BHE-1 with a coaxial construction. At the same time, this value was closest to the theoretical value of thermal conductivity of rocks λ, determined on the basis of literature. The standard deviation and the coefficient of variation confirmed that the effective thermal conductivity λeff, calculated for different time intervals, showed little variation in value. The values of effective thermal conductivity λeff for each time interval for the same borehole exchanger were similar in value. The lowest values of effective thermal conductivity λeff most often appeared for analysis with averaging every 60 min, and the highest—for analysis with averaging every 1 min. For safety reasons, when designing (number of BHEs), safer values should be taken for analysis, i.e., lower, averaging every 60 min.

scholarly journals A Study on Improving the Coefficient of Performance by Comparing Balancing Well and Standing Column Well Heat Exchange Systems

2020 ◽  
Vol 12 (24) ◽  
pp. 10445
Author(s):  
Myungkwan Lim ◽  
Kyoungbin Lim ◽  
Changhee Lee
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Effective Thermal Conductivity ◽  
Water Discharge ◽  
Underground Water ◽  
Coefficient Of Performance ◽  
Geothermal System ◽  
Heat Accumulation ◽  
Heating And Cooling ◽  
Discharge Water

This study proposed a technology to improve the performance characteristics and coefficient of performance (COP) of a geothermal system by fundamentally preventing underground water discharge and maintaining a constant temperature of the underground heat exchanger composed of bleed discharge water that utilizes two balancing wells using cross-mixing methods. Using the standing column well (SCW) and cross-mixing balancing well underground heat exchanger, we compared and analyzed the effective thermal conductivity characteristics and COP characteristics during heating and cooling modes. Consequently, the cross-mixing balancing well underground heat exchanger exhibited more effective thermal conductivity than the SCW underground heat exchanger, with a high COP. Therefore, suggesting the performance was improved using groundwater flow rather than SCW. The comparison and analysis results of the effective heat map characteristics using the results of the SCW and balancing well system showed that the heating operation for the SCW underground heat exchanger had better thermal conductivity characteristics than the cooling operation. In addition, regarding a balancing well underground heat exchanger, the cooling operation exhibited superior thermal conductivity characteristics. Thus, the performance was considered to have improved due to the flow of activated groundwater in the ground and the rapid heat transfer without heat accumulation.

scholarly journals Investigation of heat transfer enhancement in an annular conduit with angled fins using functionalized GNP colloidal suspension

2021 ◽  
Vol 945 (1) ◽  
pp. 012058
Author(s):  
Sayshar Ram Nair ◽  
Cheen Sean Oon ◽  
Ming Kwang Tan ◽  
S.N. Kazi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Colloidal Suspension ◽  
Industrial Applications ◽  
Point Of View ◽  
Solid Particles ◽  
Working Fluid

Abstract Heat exchangers are important equipment with various industrial applications such as power plants, HVAC industry and chemical industries. Various fluids that are used as working fluid in the heat exchangers such as water, oil, and ethylene glycol. Researchers have conducted various studies and investigations to improve the heat exchanger be it from material or heat transfer point of view. There have been attempts to create mixtures with solid particles suspended. This invention had some drawbacks since the pressure drop was compromised, on top of the occurrence of sedimentation or even erosion, which incurs higher maintenance costs. A new class of colloidal suspension fluid that met the demands and characteristics of a heat exchanger was then created. This novel colloidal suspension mixture was then and now addressed as “nanofluid”. In this study, the usage of functionalized graphene nanoplatelet (GNP) nanofluids will be studied for its thermal conductivity within an annular conduit with angled fins, which encourage swirling flows. The simulation results for the chosen GNP nanofluid concentrations have shown an enhancement in thermal conductivity and heat transfer coefficient compared to the corresponding base fluid thermal properties. The data from this research is useful in industrial applications which involve heat exchangers with finned tubes.

Determination of Optimum Design Parameters of Horizontal Parallel Pipe and Vertical U-Tube Ground Heat Exchangers

2009 ◽  
Author(s):  
Hakan Demir ◽  
Ahmet Koyun ◽  
S¸. O¨zgu¨r Atayılmaz
Keyword(s):  
Thermal Conductivity ◽  
Energy Consumption ◽  
Heat Exchanger ◽  
Objective Function ◽  
Heat Exchangers ◽  
Ground Heat Exchanger ◽  
Ground Source Heat Pump ◽  
Soil Thermal Conductivity ◽  
Ground Heat Exchangers ◽  
Ground Source

The most important part of a ground source heat pump (GSHP) is the ground heat exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the ground source heat pump. Soil composition, thermal properties and water content affect the length of ground heat exchanger. Another parameter affects the size of the ground heat exchanger is the shape. There are two basic ground heat exchanger configurations: vertical U-tube and horizontal parallel pipe. There are plenty of works on ground source heat pumps and ground heat exchangers in the literature. Most of the works on ground heat exchangers are based on the heat transfer in the soil and temperature distribution around the coil. Some of the works for thermo-economic optimization of thermal systems are based on thermodynamic cycles. This study covers comparative thermo-economical analysis of horizontal parallel pipe and vertical u-tube ground heat exchangers. An objective function has been defined based on heating capacity, investment and energy consumption costs of ground heat exchanger. Investment and energy consumption costs were taken into account as total cost in the objective function. The effects of the soil thermal conductivity, number of pipes, thermal capacity of ground heat exchanger, pipe diameter and the burial depth on the objective function were examined. The main disadvantage of U-tube ground heat exchanger is higher borehole cost that makes installation cost higher than parallel pipe ground heat exchanger. To make reference functions equal for both type of ground heat exchangers, the borehole cost must be under 20 $/m (now 55 $/m) for a given heating or cooling capacity. The performance of ground heat exchangers depends on the soil characteristics especially the soil thermal conductivity.

Thermomechanical Treatment of Aluminum Alloy Fin Stock for Heat Exchanger Produced by Twin Roll Strip Casting Process

2010 ◽  
Vol 638-642 ◽  
pp. 241-246 ◽  
Author(s):  
Suk Bong Kang ◽  
Dong Bae Kim ◽  
Sang Su Jung ◽  
Kwang Jun Euh
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Alloy ◽  
Heat Exchanger ◽  
Cold Rolling ◽  
Heat Exchangers ◽  
Casting Process ◽  
Strip Casting ◽  
Manufacturing Cost ◽  
Intermediate Annealing ◽  
Twin Roll

Aluminum alloys are commonly used as a material for heat exchangers due to their higher thermal conductivity and specific strength among various metallic materials. The lightweightening heat exchangers for automobile application are requisite for reducing the evolution of CO2 and improving the efficiency of fuel. The twin roll strip casting process is considered to produce the high quality and low manufacturing cost aluminum alloy fin stock for automobile heat exchangers. Thermomechamical treatment has carried out to obtain optimum processes for initial cold rolling, intermediate annealing and final cold rolling, which can meet the requirements for high strength and high thermal conductivity after brazing heat treatment. Mechanical properties and thermal condutivity have been evaluated before and after simulated brazing process. The nuclei of recrystallization might be formed along shear deformation bands during initial cold rolling and should be grown during intermediate annealing to enhance the permeation of molten brazings for the following brazing process. Final cold rolling has allowed strain hardening and controlling of sagging amount as fin stock materials of heat exchanger. In the present study the suitable thermomechnical treatment was suggested to balance the properties of strength, thermal conductivity, brazing behavior and sagging in Al-Fe-Mn-Si-Zn based alloys produced by twin roll strip casting process.

Analysis of Cryogenic Refrigeration Cycle Using Two Stage Intercooler

2010 ◽  
Vol 297-301 ◽  
pp. 1146-1151 ◽  
Author(s):  
Ho Saeng Lee ◽  
S.T. Oh ◽  
Jung In Yoon ◽  
S.G. Lee ◽  
K.H. Choi
Keyword(s):  
Natural Gas ◽  
Liquefied Natural Gas ◽  
Performance Characteristics ◽  
Coefficient Of Performance ◽  
Refrigeration Cycle ◽  
Compression Process ◽  
Methane Cycle ◽  
Two Stage ◽  
Yield Efficiency ◽  
Cycle Efficiency

This paper presents the comparison of performance characteristics for the several natural gas liquefaction cycles. The liquefaction cycle with the staged compression was designed and simulated for improving the cycle efficiency using HYSYS software. This includes a cascade cycle with a two-stage intercooler which is consisted of a Propane, Ethylene and Methane cycle. In addition, these cycles are compared with a modified staged compression process. The key parameters of the above cascade cycles were compared and analyzed. The COP (Coefficient of Performance) of the cascade cycle with a two-stage intercooler and a modified staged compression process is 13.7% and 29.7% higher than that of basic cycle. Also, the yield efficiency of LNG (Liquefied Natural Gas) improved compared with the basic cycle by 28.5%.

Improving the Energy Efficiency of Adsorption Chillers by Intensifying Thermal Management Systems in Sorbent Beds

2017 ◽  
Author(s):  
Brian K. Paul ◽  
Kijoon Lee ◽  
Hailei Wang
Keyword(s):  
Heat Exchanger ◽  
Thermal Management ◽  
Heat Exchangers ◽  
Thermal Model ◽  
Coefficient Of Performance ◽  
Management Systems ◽  
Cooling Power ◽  
Thermal Mass ◽  
Adsorption Refrigeration ◽  
Microchannel Heat Exchanger

The objective of this study was to develop a strategy for miniaturizing heat exchangers used for the thermal management of sorbent beds within adsorption refrigeration systems. The thermal mass of the microchannel heat exchanger designed and fabricated in this study is compared with that of commercially available tube-and-fin heat exchangers. Efforts are made to quantify the overall effects of miniaturization on system coefficient of performance and specific cooling power. A thermal model for predicting the cycle time for desorption is developed and experiments are used to quantify the effect of the intensified heat exchanger on overall system performance.

The Impact of Base Metal on the Thermal-Hydraulic Performance of Metal Foam Heat Exchanger for Cooling and Dehumidification Applications

2017 ◽  
Author(s):  
Kashif Nawaz ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Base Metal ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Metal Foam ◽  
Operating Conditions ◽  
Copper Metal ◽  
The Impact

In the wake of utilization of novel materials in various thermal applications open cell metal foams have received attention due to their inherent properties such as large surface area to volume ratio and higher thermal conductivity. Additionally, complex tetradecahedron structure promotes mixing and makes them a good candidate for heat transfer applications. In this paper, a relative comparison has been made between the thermal-hydraulic performance of aluminum and copper metal foam heat exchangers with the same geometry under dry and wet operating conditions. Heat exchanger consisting of round tube with annular layer of metal foam have been considered. Experiments have been conducted using a closed-loop wind tunnel to measure the heat transfer performance and pressure drop. The impact of base metal (aluminum and copper) on the heat transfer rate has been evaluated at varying air flow rates and upstream relative humidity. It has been found that due to similar geometry (flow depth, face area, pore size) both aluminum and copper foam samples have comparable pressure drop under dry conditions. However, the pressure gradient was noticeably different for two samples under wet operating conditions. An obvious difference in heat transfer rate for aluminum and copper metal foam heat exchangers was observed under both dry and wet operating conditions. The findings have been explained in terms of the impact of the thermal conductivity of base metal and condensate retention.

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