•A brief review on application of nanofluid in heat exchangers.•Presenting a review on nanofluids and their simulation methods.•Presenting studies on different heat exchangers including: plate, ...helical, shell and tube and double-tube.•Trying to understand the mechanisms of heat transfer in the field of using nanofluids in heat exchangers.•Nanofluids reduce volume of heat exchangers and improve saving energy.
In this paper a brief review on application of nanofluids in heat exchangers has been addressed. One of the barriers to increase the capacity of different industries is the lack of response of heat devices in higher capacities. In addition, increasing capacity leads to an increase in pressure drop and this is one of the most important restrictions on the large industries. Conventional methods of increasing heat transfer greatly increase the pressure drop, and according to the results of previous studies, using the special nanofluids, the thermal efficiency of the heat exchanger can be increased significantly, which is one of the most important thermal devices in the industry. In this research, firstly a review of nanofluids studies and introduction of nanofluids is presented, then their simulation methods are investigated, and finally, studies on the used tubes in the heat exchangers have been investigated, and studies of the plate heat exchanger, helical heat exchanger, shell and tube heat exchanger, and double-tube heat exchanger have been examined. The enhancement of thermal and hydraulic performance of heat exchangers is very important in terms of energy conversion, and also is important in the economic recovery of systems through savings. This paper examines previous studies on heat exchangers and using of nanofluids in them. The purpose of the paper is not only to describe the previous studies, but also to understand the mechanisms of heat transfer in the field of using nanofluids in heat exchangers, and also to evaluate and compare different heat transfer techniques. Finally, it can be concluded that the nanofluids in most cases improve heat transfer, which reduce the volume of heat exchangers, saving energy, consequently water consumption and industrial waste.
•A novel heat exchanger was designed using fin tubes as microchannels.•Flow distribution in microchannels was provided by a 3D printed manifold.•Shell-side heat transfer coefficients up to ...45,000 W/m2 K were obtained.•The heat exchanger can be scaled up in a multitube bundle for larger applications.
This paper discusses the design and performance characterization of a compact tubular manifold microchannel heat exchanger. The purpose of this study was to explore the role of more precise flow distribution in the heat exchanger utilizing an additively manufactured manifold for single-phase flow under low to moderate heat flux conditions. The heat exchanger uses a commercially available enhanced tube having a fin structure on its outer surface and helical pattern of grooves (rifling structure) on the inner bore of the tube. A 3D printed manifold made of ABS plastic was used to properly distribute the flow on the shell-side of the heat exchanger. Water was used as the working fluid for both shell and tube-sides. Single-phase experimental tests showed an overall heat transfer coefficient of 22,000 W/(m2K) and shell-side heat transfer coefficient of 45,000 W/(m2K) for the shell-side and tube-side water flow rates of 82 g/s and 806 g/s, respectively. The shell-side heat transfer coefficient was found to be an order of magnitude higher than that found in typical shell and tube and plate-type heat exchangers.
•HDPE polymer HX is fabricated using layer-by-layer line welding of plastic sheets.•Experimental testing of the HX has been successfully performed.•The polymer-based wall thermal resistance is no ...longer the limiting factor.•The polymer HX shows superior air-side performance over plane plate fin surface.
In addition to their low cost and weight, polymer heat exchangers offer good anticorrosion and antifouling properties. In this work, a cost effective air-water polymer heat exchanger made of thin polymer sheets using layer-by-layer line welding with a laser through an additive manufacturing process was fabricated and experimentally tested. The flow channels were made of 150μm-thick high density polyethylene sheets, which were 15.5cm wide and 29cm long. The experimental results show that the overall heat transfer coefficient of 35–120W/m2K is achievable for an air-water fluid combination for air-side flow rate of 3–24L/s and water-side flow rate of 12.5mL/s. In addition, by fabricating a very thin wall heat exchanger (150μm), the wall thermal resistance, which usually becomes the limiting factor on polymer heat exchangers, was calculated to account for only 3% of the total thermal resistance. A comparison of the air-side heat transfer coefficient of the present polymer heat exchanger with some of the commercially available plain plate fin heat exchanger surfaces suggests that its performance in general is superior to that of common plain plate fin surfaces.
•Heat and mass transfer comparisons of desiccant coated microchannel and fin-and-tube heat exchangers were analyzed.•The heat transfer coefficient of DMHE is almost twice that of DFHE.•The mass ...transfer coefficient of DMHE is larger than that of DFHE by 15%.•Microchannel type shows excellent heat and mass transfer capacities at the cost of high pressure drop.
Two types of DCHEs, desiccant coated microchannel heat exchanger (DMHE) and desiccant coated fin-and-tube heat exchanger (DFHE), are manufactured and tested. The heat transfer, mass transfer and pressure drop performances of two DCHEs are analyzed and compared by experimental results. In the same conditions, the heat transfer coefficients of DMHE are almost twice as large as those of DFHE, no matter for sensible heat or latent heat. In dehumidification, the ratios of latent heat to total heat for DFHE and DMHE are 90% and 83%, separately. In regeneration, the ratios of latent heat to total heat for two DCHEs are both approximately 60%. The mass transfer coefficient of DMHE is 15% larger than that of DFHE. The pressure drops per unit transfer area of DMHE is almost 125% larger than that of DFHE. In a conclusion, DMHE shows lower heat capacity, higher heat and mass transfer capacity compared with DFHE.
•PCHE’s model Incorporating actual channels geometries have been developed.•The performance of PCHEs has been evaluated using different channel geometries.•The effects of PCHE designs on the cycle’s ...performance have been reported.•Efficient designs for the PCHE’s have been suggested that enhance the cycle’s efficiency.
Several fin configurations have been proposed in the literature to address the poor hydraulic performance associated with the PCHEs. However, the effect of the heat exchangers with proposed channel geometries on the performance of supercritical carbon dioxide(sCO2) power cycle is missing. In this context, the current study deals with the effects of different designs of the PCHEs varied by proposed channel configurations, heat exchanger’s effectiveness and design value of inlet Reynolds number on the performance of sCO2 power cycle. Moreover, a multi-object optimization study to find the best bargain between cycle’s efficiency and heat exchanger’s size is carried out using five different fin configurations (straight, zigzag, C-shaped, S-shaped, and airfoil fin channel configuration), heat exchanger’s effectiveness and inlet Reynolds number as a design variable. Results shows that enhancement in the hydraulic characteristics for a channel geometry that comes at the cost of thermal performance may not benefit the system’s efficiency. Optimization results suggest that C-shaped channel and zigzag channel geometries correspond to the cycle’s maximum efficiency and heat exchanger’s minimum size respectively. Optimization results further highlight that the comparison of channel geometries should be performed while in the setting of complete power generation cycle to account for all the variables involved.
The cost of heat exchangers account for a large proportion of total investment in organic Rankine cycle (ORC). In this paper, plate heat exchanger (P), shell-and-tube heat exchanger (S) and ...finned-tube heat exchanger (F) are used as evaporator and condenser of four subcritical ORC configurations: ORC-PP, ORC-SS, ORC-FP and ORC-FS. The thermo-economic models are built and a thermo-economic evaluation and comparison of four ORC configurations is presented in order to recover the low-temperature waste heat. The optimal evaporating pressure, pinch point temperature difference, net power output and dynamic payback period corresponding to the minimum electricity production cost (EPC) are obtained for different ORC configurations under different heat source temperatures. Results show that the EPCs of ORC-PP and ORC-SS are apparently higher than that of ORC-FP and ORC-FS. Among them, ORC-FS is the most cost-effective configuration. The optimal pinch point temperature difference in evaporator has a decreasing trend with the increase of critical temperature of working fluid for ORC-FS and ORC-FP, while the optimal pinch point temperature difference in condenser keeps nearly constant.
•Performing thermo-economic modeling of different ORCs (organic Rankine cycles).•Comparing thermo-economic performance of ORCs based on different heat exchangers.•ORC adopting FS configuration turns out to be the most cost-effective.•Sensitivity analysis on EPC and ppd is conducted.
A novel particle-to-fluid direct-contact counter-flow heat exchanger (PFDCHX) is introduced and investigated. The proposed heat exchanger offers efficient integration with an air-breathing power ...cycle. A proposed particle-based power tower integrated system using the PFDCHX is presented. The PFDCHX system comprises two main parts: the particle handling unit (PHU) and the direct-contact heat exchanger (DCHX). The PHU delivers solid particles to the pressurized DCHX, a manifold assembly was deployed to separate particles into several separate streams to be injected at the upper end of the DCHX via several distributor pipes. Several enhancement features were considered to prevent particle carryover, including a tangential inlet for the pressurized air (at the bottom end of the DCHX), particle–air disengagement zone (at the top end of the DCHX), and a tapered-shaped heat exchange chamber. Results showed that, for tests with excessive particle flow rate, more than 80% of the temperature rise was achieved within 0.35 m above the air inlet, attributed to the tangential inlet’s swirl flow pattern. The overall temperature rise along the heat exchanger was not significantly influenced by a change in operating air pressure from one barg to three barg.
•A novel particle-to-air direct-contact heat exchanger is introduced-investigated.•The added features overcome issues in the previous direct-contact heat exchangers.•More than 80% of heat transfer occurred at 0.35 m above the air inlet.•The temperature rise didn’t change with varying the operating air pressure.•The proposed heat exchanger can be integrated effectively-safely with power cycle.
•Heat transfer performance of nanofluids in a plate heat exchanger is investigated.•The maximum enhancement in average Nu is 22.6% for 1.0 wt.% Fe3O4-water nanofluid.•The optimum concentration for ...thermal enhancement is 0.5 wt.% for CuO nanofluid.•Empirical formulas of experimental Nu are derived based on experimental data.•Fe3O4-water nanofluid is a promising heat transfer medium for solar energy systems.
In this paper, a corrugated plate heat exchanger in solar energy systems is used to investigate heat transfer and fluid flow characteristics of various nanofluids. By adding various nanoparticles (Al2O3-30 nm, SiC-40 nm, CuO-30 nm and Fe3O4-25 nm) into the base fluid, effects of nanofluid types and particle concentrations (0.05 wt.%, 0.1 wt.%, 0.5 wt.% and 1.0 wt.%) on the thermal performance of the plate heat exchanger are analyzed at flow rates in the range of 3–9 L/min. Results indicate that both heat transfer enhancement and pressure drop for nanofluids show significant increases compared to the base fluid. The Fe3O4-water and CuO-water nanofluids show the best and the worst thermal performances of the plate heat exchanger, respectively. When 1.0 wt.% Fe3O4-water nanofluid is used as the working fluid, compared to DI-water, the convective heat transfer coefficient is increased by 21.9%. However, an increase of 10.1% in pressure drop is obtained for the 1.0 wt.% Fe3O4-water nanofluid. Finally, empirical formulas of experimental Nusselt number are obtained based on the experimental data. A new way to predict the thermal performance for various nanofluids in heat transfer systems is provided.
•Provide precise pressure and temperature distributions along the full length of the SCO2 PCHE.•SCO2 PCHX performance with different fin configurations has been reported for a wide range of Reynolds ...numbers.•This study will be significant to understand the behavior of SCO2-PCHEs at high Reynolds numbers.
The numerical study of thermal and hydraulic performance of a supercritical CO2 (SCO2) printed circuit heat exchanger (PCHE) has been conducted and validated using published experimental data. A domain optimization study has been carried out to finalize a PCHE domain with significantly reduced computational time without compromising the accuracy of the solution. The optimized domain was used to evaluate the thermal and hydraulic performance of the heat exchanger with a wide range of Reynolds numbers and different geometrical configurations. In contrast to subcritical region, thermophysical properties of CO2 undergo sharp variations close to the critical point. In order to capture the swift variation in thermophysical properties of CO2 and to ensure accurate prediction of thermal and hydraulic performance of heat exchanger, properties of SCO2 were computed using REFPROP. MATLAB was linked through a script to REFPROP and high-resolution real gas property (RGP) file was generated and supplied to a commercial code ANSYS-CFX for numerical simulations.
An innovative adsorber plate heat exchanger (APHE), which is developed for application in adsorption heat pumps, chillers and thermal energy storage systems, is introduced. A test frame has been ...constructed as a representative segment of the introduced APHE for applying loose grains of AQSOA-Z02. Adsorption kinetic measurements have been carried out in a volumetric large-temperature-jump setup under typical operating conditions of adsorption processes. A transient 2-D model is developed for the tested sample inside the setup. The measured temporal uptake variations with time have been fed to the model, through which a micro-pore diffusion coefficient at infinite temperature of 2 E−4 m2s−1 and an activation energy of 42.1 kJ mol−1 have been estimated. A 3-D model is developed to simulate the combined heat and mass transfer inside the APHE and implemented in a commercial software. Comparing the obtained results with the literature values for an extruded aluminium adsorber heat exchanger coated with a 500 μm layer of the same adsorbent, the differential water uptake obtained after 300 s of adsorption (8.2 g/100 g) implies a sound enhancement of 310%. This result proves the great potential of the introduced APHE to remarkably enhance the performance of adsorption heat transformation appliances.
•An innovate stainless steel adsorber plate heat exchanger (APHE) is introduced.•Representative APHE-segment is experimentally tested with AQSOA–Z02 loose grains.•2-D and 3-D Simulations carried out on the representative segment and the APHE.•Diffusion coefficient at infinite temperature (D∞) and (Ea) are obtained.•Performance of the introduced APHE outreaches coated aluminium heat exchangers.
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