Coupling effect between tunnel lining heat exchanger and subway thermal environment

Design of heat exchanger for the production of zinc imidazole framework-8 (ZIF-8) particles

Modelling and optimization of a forced convection heat exchanger for Mars waste heat rejection for power cycle and cryocooling applications

Performance and life cycle assessment of pillow plate heat exchanger utilizing microencapsulated phase change material slurry

Thermal performance of a 10-kW phase-change plate heat exchanger with metal foam filled channels

Additive manufacturing (AM) can enable complex and novel designs that are otherwise infeasible with traditional metal manufacturing techniques. In low-volume production scenarios, particularly for specialized applications which can benefit from customized designs, traditional metal manufacturing techniques may be limited by costs associated with tooling. The ability to produce novel designs is particularly interesting in heat exchanger (HX) design where performance is often largely based on the achievable geometry. However, consequences of the AM process such as surface roughness, deviation from specified dimensions, and defects such as cracks and voids could also affect HX performance. These effects may vary between identically designed AM parts based on AM machine settings. The goal of this work is to gain a better understanding of the performance variations across several different implementations of the same heat exchanger design. More specifically, the objective of this work is to experimentally compare the thermal and hydraulic performances of a traditionally manufactured, stamped-aluminum aircraft oil cooler and three geometrically equivalent, additively manufactured counterparts. Compared to the traditionally manufactured heat exchanger, the AM HXs exhibited significantly higher air-side pressure loss and higher heat transfer despite having nominally similar geometries. Between AM HXs, there were slight differences in surface roughness characteristics based on optimal profilometry measurements. In addition, the thickness of the air-side fins varied as much as 15 percent between the AM HXs. The net effect, without the contribution of each cause clear, was higher air-side pressure loss and slightly higher heat transfer for the AM HX with thicker fins. This study indicates that functional heat exchangers built using AM vary in performance even when the same digital model is used to print them, and that AM HXs as a group perform considerably differently than their traditional counterparts. Thus, there is a need to account for anticipated surface roughness, geometric deviations, and potential defects when designing HXs. Proper consideration could result in improved thermal performance for future heat exchangers.

The number of products benefiting from micro components in the market is increasing, and consequently, the demand for well-matched tools, equipment and systems with micro features is eventually increasing as well. During the design process of micro products, a number of issues ap- pear which are inherent due to the down scaling or physical phenomena dominating in the micro range but negligible in the macro scale. In fact, some aspects in design for micro manufacturing are considerably different compared to the de- sign procedure taken at the macro level. Identifying the differ- ences between design considerations at micro compared to macro scale, and defining potential guidelines based on them, provides an opportunity to modify the conventional design methodologies towards becoming micro specific. In this pa- per, the need for a micro-oriented approach for designing mi- cro products which has not been investigated hitherto studied. For this purpose, an additional step named "Rules To Consider" (RTC) is added to the conventional design method- ologies.Thisstepisconstituted based onthe feedbacks gained during analyzing the different iterations of the design. The knowledge obtained during the design process of a micro product can be added to the RTC unit, and this unit becomes enriched progressively in design process of similar micro products and supplemented to the conventional design meth- odologies to be served as a micro-oriented design methodol- ogy. Inorder to present the application ofRTC unit, the design process of a micro heat exchanger is investigated. Manufacturability and functional performance are considered as evaluation criteria, and the lessons learned from each de- sign iteration and evaluation are employed in the subsequent design proposals until an acceptable design is achieved. Thermal performance of the heat exchangers is evaluated using finite element (FE) simulation of the conjugate heat transfer. The design proposals are optimized in terms of geo- metricaldimensions,andasensitivityanalysisisconductedon the mass flow rate and heat generation power in the heat source. Finally, the designs with higher thermal performance and manufacturability are introduced. The result of the ther- mal analysis reveals the fact that the presence of the fins and modification of their dimensions as well as the constituent material for fabricating the micro heat exchanger do not sig- nificantly improve the thermal performance of the micro heat exchangers. This is an interesting outcome which can result in considerable reduction of the manufacturing costs by simpli- fying the geometrical design of the heat exchanger. The micro-specificdesignconsiderationswhich are extracted from the design process of the micro heat exchanger are added to the RTC unit and can be applied as guidelines in design pro- cess of any other micro heat exchanger. In other words, the current study can provide a useful guideline in design for manufacturing of micro products.

Long-term performance of a front-end capillary heat exchanger for a metro source heat pump system

Chapter 3 - Heat exchanger for solar thermal energy

Improved tube structure and segmental baffle to enhance heat transfer performance of elastic tube bundle heat exchanger

For economic reasons, the optimal design of heat exchanger is required. Design of heat exchanger is usually based on the iterative process. The design conditions, equipment geometries, the heat transfer and friction factor correlations are totally involved in the process. Using the traditional iterative method, many trials are needed for satisfying the compromise between the heat exchange performance and the cost consideration. The process is cumbersome and the optimal design is often depending on the design engineer’s experience. Therefore, in the recent studies, many researchers, reviewed in [1], applied the genetic algorithm (GA) [2] for designing the heat exchanger. The results outperformed the traditional method. In this study, the alternative approach, algorithm of changes, is proposed for optimal design of shell‐tube heat exchanger [3]. This new method, algorithm of changes based on I Ching (???), is developed originality by the author. In the algorithms, the hexagram operations in I Ching has been generalized to binary string case and the iterative procedure which imitates the I Ching inference is also defined. On the basis of [3], the shell inside diameter, tube outside diameter, and baffles spacing were treated as the design (or optimized) variables. The cost of the heat exchanger was arranged as the objective function. Through the case study, the results show that the algorithm of changes is comparable to the GA method. Both of method can find the optimal solution in a short time. However, without interchanging information between binary strings, the algorithm of changes has advantage on parallel computation over GA.

Nowadays ensure the performance of heat exchanger is one of the toughest roles in industries. In this work focused on improve the performance of shell and tube heat exchangers by reducing the pressure drop as well as raising the overall heat transfer. This work considered as a different nanoparticles such as Al2O3, SiO2, TiO2, and ZrO2 to form a nanofluids. This nanofluids possesses high thermal conductivity by using of this increase the heat transfer rate in shell and tube heat exchanger. The selected nanofluids are compared to base fluid based on the thermophysical properties as well as heat transfer characteristics. All the heat transfer characteristics are improved by applying of nanofluids particularly higher results are obtained with using of TiO2 and Al2O3 compared to SiO2 and ZrO2. Mixing of nanoparticles increased in terms of volume percentage it will be increases the all heat transfer characteristics as well as performance of the heat exchanger.

Design and CFD analysis of hair pin heat exchanger using aluminium and titanium carbide nanofluids

Enhancement of the heat transfer coefficient is important for the design and operation of heat exchangers. In this study, a numerical model is built to investigate the performance of spray cooling heat exchanger as water is sprayed on a horizontal tube. The objectives of the study are 10 evaluate evaporation rate of the falling water film on a horizontal tube evaporator and obtaining the effect of the distance from the nozzle to the hot tube locution on the proportion rule and on heat transfer effectiveness. Moreover, the effect of droplet size distribution and the hot tube surface superheating temperature on the evaporation rate are also conducted. For a certain distance from nozzle distributor to the hot tube surface and by using the equations of mass, momentum and energy of the sprayed droplets, the change in droplet velocity, droplet size and its temperature can be evaluated. Vapor film is created around the hot tube surface. In this study, the formed vapor layer Thickness around the hot surface, evaporation rate and heat transfer effectiveness were also evaluated. The heat transfer characteristics are investigated at the considered ranges of the various spraying parameters such as: sprayed mass velocity (sprayed mass flow rate per the unit area of the lest tube) which ranged from 1.2532 101.5314 kg/m2.s, droplet size (ranged from 128.4 10 300 m), (droplet velocity (ranged from 310 7.43 m/s ) and spruce droplet size (ranged from 70 to 70 oC). The results show that the evaporation rate and the free transfer effectiveness are mainly increased by increasing the smile temperature. Also, the evaporation rule and the heat transfer effectiveness are increased by decreasing the droplet velocity. Al high initial sprayed mass velocity, hic vapored mass flow rate and the heat transfer effectiveness are inversely proportional to the droplet size. There is an optimum distance from nozzle distributor to the rube surface location of which the maximum evaporated rate will occur. The comparison between the obtained results and the results one to others shows a good agreement in which the difference between these results was ranged from 4 to15%

Theoretical prediction of longitudinal heat conduction effect in cross-corrugated heat exchanger

Numerical investigations of the tunnel environment effect on the performance of energy tunnels