Aluminum Heat Exchangers Research Articles

Water sorption property and cooling performance using natural mesoporous siliceous shale impregnated with LiCl for adsorption heat pump

The composite adsorbent of natural mesoporous powder of Wakkanai siliceous shale (WSS) impregnated with LiCl has been investigated. In this study, the slurry of WSS–LiCl with acryl resin as a binder was prepared for fabricating an adsorbent-filled heat exchanger (HEX). The optimal LiCl content for the impregnation with WSS was 20 wt%, which was chosen from the relation between water uptake and pore volume. The theoretical sorption amounts were estimated from various sorption isotherms, and the value was 0.34 g/g at the temperature conditions of 80 °C (regeneration), 30 °C (condensation and adsorption), and 15 °C (evaporation). From the analysis of sorption heat, it was found that water adsorption and desorption occurred repeatedly at the lower region of 45–50 kJ/mol at the driving conditions for the adsorption heat pump. To evaluate the coefficient of cooling performance (COP) and a specific cooling power (SCP), the adsorbent-filled HEX was prepared using a small-sized corrugated-fin-type aluminum HEX and the slurry. The COP and SCP were 0.41 and 498 W/kg at 80 °C of regeneration, respectively.

Passive cooling of Li-Ion cells with direct-metal-laser-sintered aluminium heat exchangers filled with phase change materials

Operating Li-Ion cells at adverse temperatures can lead to performance decrease and faster ageing effect. A thermal management system (TMS) designed to guarantee the cells isothermal condition is therefore necessary. Phase Change Materials (PCM) can form part of an efficient TMS based on passive cooling. However, when Li-Ion cells are exposed to extreme electrical regimes, PCMs cannot recover all of the latent heat due to their low thermal conductivity. This study experimentally investigates the isothermal performance of PCMs integrated with Direct-Metal-Laser-Sintered (DMLS) aluminium heat exchangers (HEX) as a passive TMS. The DMLS HEXs are employed to enhance the equivalent thermal conductivity of the TMS and thermally connect the Li-Ion cell to the PCM. The TMS performance is evaluated in terms of cell average surface temperature and temperature uniformity. Single and consecutive cycles at different discharge rates are imposed to simulate intermittent and constant loads. To assess the TMS sensitivity to the thermal boundary conditions, the HEX is either insulated or surrounded by the ambient air. Under single discharge cycles, the cell temperature rise and temperature disuniformity decrease using the PCM HEX in both thermal boundary conditions compared to relying on air natural convection. Under consecutive cycles, the temperature rise is minimised when the PCM HEX is not insulated. These results show that PCMs show great potential as a passive TMS for a variety of Li-Ion cells’ operating conditions. However, the optimisation of the PCM-TMS design is found to be case-dependent.

Experimental study of a hybrid solar photovoltaic, thermoelectric and thermal module

Nowadays, solar energy, which can be photovoltaic and thermal, is a clean and reliable source of energy for the production of electric and thermal power. However, new ways for improving photovoltaic efficiency are fundamental for an extensive application of this technology. Most of the energy absorbed by the PV panel converts itself into heat, which usually is lost and does not have any energetic value. The performance of a combined photovoltaic (PV), thermoelectric generator (TEG) and water heating panel is tested in practice. The thermoelectric set is applied on the back of the PV panel so that the two devices have approximately the same temperature. On the other face of the thermoelectric set, there is the water heating panel, which consists of an aluminium heat exchanger specially designed for this hybrid module. The exposed surface of the hybrid panel has an area of about 2.72 dm2. Experimental tests were conducted in direct solar exposure during July. The experimental results indicate that the maximum global module efficiency was 91.3% for an irradiance of 1089 W/m2. The power peak production was 29.7 W, at 2 p.m., with an irradiance value of 1230 W/m2.

Experimental Tests of Natural Gas Samplers Prior to Mercury Concentration Analysis

Mercury (Hg) is a natural, trace component of natural gas. Corrosion of aluminum heat exchangers by liquid metallic Hg can lead to dramatic issues. The quantification of gaseous Hg concentration in natural gas streams is therefore crucial prior to the implementation of Hg removal units for preventing the formation of liquid Hg. Different methodologies exist for the determination of Hg concentration in natural gas, one of which relies on the sampling of natural gas at high pressure using stainless-steel cylinders prior to off-site Hg measurement. An inert internal coating is supposed to hamper Hg adsorption, presumably making the Hg analysis reliable. Here, we challenge this statement by showing that even silicon-coated cylinders are inefficient for preventing Hg adsorption on internal walls. Different cylinders were tested for gaseous Hg concentration stability over time in a clean Argon matrix. We find that gaseous Hg concentration sharply declines in almost all tested cylinders (uncoated, PTFE-coated an...

An innovative method of applying fluxes using the low-pressure cold gas spraying method

In the paper, the results of tests of flux application for aluminum brazing processes using the low-presure cold gas spraying method, are presented. It was pointed out that this method could be used as an alternative to current methods of flux application, among others in the production of aluminum heat exchangers. The results of wettability tests made with braze spreading method on fluxed substrates and metallographic investigations of brazed joints are presented. Good quality of brazed joints without incompatibilities and good mechanical properties have been demonstrated.

Improvement of corrosion penetration resistance for aluminum heat exchanger by alloying zirconium

Corrosion of the aluminum multi-port extrusion (MPE) leads to heat exchanger leakage. Corrosion of the 1xxx series aluminum MPE tubes proceeds continuously along Al13Fe4, which is the precipitation phase of Fe impurity. The continuous corrosion behavior along Al13Fe4 rapidly propagates into the aluminum MPE tube, thereby reducing the penetration life. In this study, Zr was added in order to control the dispersion of Al13Fe4 precipitates in an attempt to improve the corrosion resistance of A1070 aluminum MPE tubes for heat exchangers. The refinement and dispersion of Al13Fe4 phase was controlled by the addition of Zr, which is a highly insoluble element in aluminum. Zr plays a role in increasing nucleation and inhibiting the growth of the surrounding Al13Fe4 phase during the precipitation to Al3Zr phase. As a result, the size of the Al13Fe4 phase became finer and more dispersed, and the continuous corrosion tendency was decreased. Therefore, corrosion propagation of aluminum MPE tube progressed uniformly and penetration was suppressed.

Condensation frosting on meter-scale superhydrophobic and superhydrophilic heat exchangers

Frost formation on heat transfer equipment such as air-source heat pump evaporators can result in drastic efficiency penalties. The performance reduction is a result of the insulating nature of ice and the increased fan power required to pump air through the constricted channels between frosted fins. Furthermore, the need to defrost adds appreciable energy use to the system. In this study, we develop a nanoengineered coating process that can be scalably applied to meter-scale, fully-assembled, aluminum heat exchangers. We demonstrate the coating on a decimeter-scale copper-tube aluminum-fin commercial heat exchanger having a 25 × 15 cm face area, and 9 corrugated fins per inch. The frosting characteristics on the unaltered heat exchanger are compared to identical components with superhydrophobic and superhydrophilic coatings for a range of inlet coolant temperatures (−5 to −10 °C) and ambient humidities (30 to 50%). The results show that a superhydrophobic heat exchanger can decrease frost accumulation, maintain heat transfer rates above half of the maximum capacity three times longer, reduce the required defrosting time and energy by 50%, and reduce the amount of water retained by 75% when compared to its uncoated and superhydrophilic counterparts.

Comments on “Experimental study on thermal–hydraulic performance of a wavy fin-and-flat tube aluminum heat exchanger”

These comments are presented to increase the awareness among the readers of Applied Thermal Engineering. Comments are presented in particular on the paper by Dong et al. (2013) where the authors investigated experimentally the air side thermal-hydraulic performance of a wavy fin-and-flat tube aluminum heat exchanger. Dong et al. (2013) did not mention some available thermal-hydraulic correlations in the literature like thermal-hydraulic correlations of Awad and Muzychka (2011). In addition, Dong et al. (2013) developed air-side friction and heat transfer correlations for wavy-fin compact heat exchangers. Their Fanning friction factor (f) and Nusselt number (Nu) correlations have six unknowns (one constant and five exponents). On the other hand, thermal-hydraulic correlations of Awad and Muzychka (2011) have only one unknown (the fitting parameter in the asymptotic model). For the aim of calculation and design of air cooled compact wavy fin wavy-fin heat exchangers, having only one unknown in thermal-hydraulic correlations of Awad and Muzychka (2011) is better than having six unknowns in thermal-hydraulic correlations of Dong et al. (2013).

Study of the corrosion rate of the paths walls of aluminum heat exchangers in the ethylene glycol antifreezes environment under developed aeration of power fluid

AnnotationAn experimental and theoretical research work on the corrosion processes of heat exchanger channels made from different aluminum alloys in an ethylene glycol antifreeze environment conducted by the authors is described in the article. The hydrodynamic simulation of the flow in the paths was performed. Significant effects of the aeration of the power fluid, the possibility of electrochemical corrosion are proved. The comparative of anti-corrosion property of different aluminum alloys is shown when operating in a wide range of power fluid velocities and temperatures.

Study of the corrosion rate of the paths walls of aluminum heat exchangers in the ethylene glycol antifreezes environment under developed aeration of power fluid

AnnotationAn experimental and theoretical research work on the corrosion processes of heat exchanger channels made from different aluminum alloys in an ethylene glycol antifreeze environment conducted by the authors is described in the article. The hydrodynamic simulation of the flow in the paths was performed. Significant effects of the aeration of the power fluid, the possibility of electrochemical corrosion are proved. The comparative of anti-corrosion property of different aluminum alloys is shown when operating in a wide range of power fluid velocities and temperatures.

Thermal and acoustic performance of an integrated automotive thermoelectric generation system

In recent years, the use of thermoelectric generators (TEGs) to recover secondary energy from exhaust heat has increased speedily with applications ranging from microwatts to kilowatts. In terms of automotive exhaust system, there are compatibility problems among automotive TEG, catalytic converter and muffler. An integrated automotive thermoelectric generator (IATEG) which contains automotive TEG, catalytic converter and muffler that converts engine exhaust waste heat into electricity is constructed and simulated. Through comparison of steel, aluminum and copper heat exchangers, it is found that both the average interface temperature and the maximum output power increase are highly dependent on the thermal conductivity of the heat exchanger material. An engine bench test and an acoustic bench test are developed to analyze the performance of the IATEG system characteristics, which are undertaken to assess the feasibility of automotive applications. The numerical simulations and experiment results indicate that the IATEG has better sound reduction performance in high frequency noise and higher temperature distribution which can generate a high power while the power output of the TEG can reach 515 W. Through these experiments, thermal, electrical and acoustic performance of the system is characterized. The results establish the fundamental development of IATEG system that enhances the TEG efficiency for vehicles.

알루미늄 열교환기가 적용된 함체 냉각용 에어컨의 성능에 대한 실험적 연구

Heat generated in a telecommunication cabinet keeps increasing due to the increased usage of mobile devices. Inadequate cooling mechanism leads to rise in the cabinet temperature, which results in the malfunction of the electronic devices. In this study, three air-conditioning unit samples one with fin-and-tube heat exchangers (Sample A) and the other two with aluminum heat exchangers having different size (Sample C with the condenser size 47% larger than that of Sample B) were designed, and tested using R-22. Tests were conducted while changing the amount of refrigerant charge, and the performance results were compared with those of foreign product (Base) running by R134a. The optimum change amount was 1250 g for Sample A and 450g for Samples B and C, 64% less charge for samples with aluminum heat exchangers. At the optimum charge, the cooling capacity of sample A was 99% of that of the Base, 105% for Sample B and 106% for Sample C. The larger cooling capacity for Samples B and C may have been due to the usage of high performance aluminum heat exchangers. The power consumption was largest for Sample A followed by Samples B and C. The smallest power consumption for Sample C may be explained by the lowest condensation pressure among the three. The COP of Sample A was 97% of that of Base, 109% for Sample B and 128% for Sample C.

Numerical Simulations of Fluid Flow and Heat Transfer through Aluminum and Copper Metal Foam Heat Exchanger – A Comparative Study

This article discusses about a numerical simulation of a metal foam heat exchanger system carried out by a commercial software. A metal foam layer is attached to the bottom of the heat exchanger to absorb heat from the exhaust hot gas leaving the system. Two types of metal foams with two different pores per inch (PPI) values are considered for heat transfer enhancement. Similarly, two different materials Aluminum and copper, that poses high thermal conductivity, metal foams are considered for the present numerical simulations. The heat exchanger system is simulated over a range of 6–30 m/s fluid velocity. The proposed simulations are compared with theoretical and experimental data available in the literature. The goal is to improve the thermal performance of the heat exchanger by decreasing the pressure drop and maximizing the heat transfer rate. Finally, it has been noticed that the velocity of the fluid decreases as PPI increases at the expense of its pressure drop. The copper metal foam gives a maximum increase of 4–10% heat transfer rate compared to aluminum metal foams for a fluid velocity of 30 m/s.

열교환기용 알루미늄 관재의 하이드로포밍 공정 적용을 위한 자유 팽창 유한요소해석과 실험적 검증

열교환기용 알루미늄 관재의 하이드로포밍 공정 적용을 위한 자유 팽창 유한요소해석과 실험적 검증

Fabrication of a superhydrophobic surface with fungus-cleaning properties on brazed aluminum for industrial application in heat exchangers

Extensive research has been carried out concerning the application of superhydrophobic coating in heat exchangers, but little is known about the application of this technique to brazed aluminum heat exchangers (BAHEs). In this work, we describe a new superhydrophobic coating method, which is suitable for BAHE use on an industrial scale. We first render the BAHE superhydrophobic by fabricating micro/nanostructures using solution dipping followed by fluorination. After the complete removal of the silicon residue, we verify using surface analysis that the BAHE surface is perfectly superhydrophobic. We also studied the fungus-cleaning properties of the superhydrophobic surface by growing fungus for 4 weeks in a moist environment on BAHE fins with and without superhydrophobic coating. We observed that, whereas the fungus grown on the untreated fins is extremely difficult to remove, the fungus on the fins with the superhydrophobic coating can be removed easily with only a modest amount of water. We also found that the coated BAHE fins exhibit excellent resistance to moisture. The superhydrophobic coating method that we propose is therefore expected to have a major impact in the heating, ventilating and air conditioning industry market.

Development of High Corrosion Resistance Hydrophobic Layers on Aluminum Immersed in Saline Geothermic Media

Anodizing processes are widely well-known processes to increase corrosion resistance and to modify the surface features of aluminum alloys. The anodizing parameters of aluminum such as electrolytes, applied current density and processing time in conjunction with the incorporation of a fluoropolymer compound were investigated to obtain thin and uniform layers of aluminum oxides resistant to saline geothermic media. The morphology of anodized films was assessed by using scanning electron microscopy. According to electrochemical impedance analysis, the incorporation of a FP to the anodized aluminum significantly increased the impedance resistance due to the formation of a hydrophobic layer on the surface of the anodized aluminum with high contact angle values. This hydrophobic processing was applied in an aluminum heat exchanger which is intended to be used in real geothermic conditions. The long-term corrosion resistance of the hydrophobic layer represents a good alternative to enhance the electrochemical properties of anodized aluminum alloys.

A coupled finite volume & discrete element method to examine particulate foulant transport in metal foam heat exchangers

The exorbitant costs associated with particulate fouling necessitates the need to formulate advanced methods to comprehend mass transport and fouling in heat exchangers. A coupled finite volume and discrete element method is developed to investigate the mechanisms that govern particle-laden gas flows and particulate fouling in idealized porous metal foam heat exchangers. This meticulous examination will take great precedence in addressing the negative impact particulate fouling has in the industry. The numerical method will permit engineers to better optimize porous metal foams for applications such as air-cooled heat aluminium heat exchangers. The robustness of this numerical method is validated against the original and modified Darcy-Forchheimer analytical equations through a novel modified porosity theory. Good agreement is obtained between the numerical and analytical results. It is shown that both 2D and 3D heat exchanger configurations of identical porosities with different geometric profiles have shown similar deposition fraction and pressure drop magnitudes albeit having a slightly different fouling layer distribution. This is attributable to the particle properties and the variation between the 2D and 3D inlet injection plane surface area. It is found that the commencement of sandstone and sawdust deposition in a 6-pore configuration differs by 0.57s, whereas a three pore configuration completely nullifies particulate fouling irrespective of foulant type. A staggered row configuration has shown significant reduction in pressure drop as compared to the 6-pore heat exchanger configuration. For the case of sandstone particles, the optimum heat exchanger geometry exhibits 78% less pressure drop and 100% less deposition fraction compared with the original 6-pore configuration.

Thermal dissipation performance of metal-polymer composite heat exchanger with V-shape microgrooves: A numerical and experimental study

Nowadays, power consumption and heat output problems are becoming more and more serious with the rapid development of multi-functional and high integration density systems. The installation space for heat exchangers is also getting smaller and smaller. Thus, the need for efficient thermal dissipation performance within limited space becomes one of the major topics in this field. In this paper, a new kind of metal-polymer composite heat exchanger with V-shape microgrooves is proposed. The physical model and governing equation of it are established under several suitable assumptions. The influences of some key factors (half apex angle, thermal conductivity coefficient, radiant emissivity, etc.) on thermal dissipation performance of metal-polymer composite heat exchanger are investigated by numerical computation method. Furthermore, a comparison of the thermal dissipation performances between commercial aluminum heat exchanger and metal-polymer composite heat exchanger with V-shape microgrooves is performed. Results show that although the spatial volume of metal-polymer composite heat exchanger is only one-fifth of that of aluminum heat exchanger, their thermal dissipation performance is almost the same. As metal-polymer composite heat exchanger has the advantages of high processing efficiency, low cost, light weighted and space saving, it will play an important role in the field of heat exchanger undoubtedly in the near future.

Experimental study and analysis of air heating system using a parabolic trough solar collector

ABSTRACTAn experimental study of air heating system was carried out using a parabolic trough collector with a U-tube aluminium heat exchanger. An evacuated tube placed at the focal length of the parabolic trough collected the solar radiations reflected from the surface of parabolic trough. The air was used as a working fluid, which was heated by passing it through a U-shaped aluminium heat exchanger placed inside the evacuated tube. It was found that efficiency of the parabolic trough collector depends on the mass flow rate, solar intensity and use of fins. It was observed that by using fins at a high mass flow rate of 4.557 kg/h, the maximum temperature of 126°C was achieved which is 13.27% more than the maximum temperature obtained without fins. Furthermore, for a low-mass-flow rate of 1.69 kg/h, the maximum temperature obtained was 149°C.

Experimental Study on the Airside Performance of Aluminum Heat Exchangers Having Slim Louver Fins

Experimental Study on the Airside Performance of Aluminum Heat Exchangers Having Slim Louver Fins