Outlet Water Temperature Research Articles

Thermal environment and waste heat recovery of high-radiant heat workshop

The high temperature of the high radiant heat reservoir workshop, the poor working environment of workers, and the long-term heat stress will hinder the brain power and cardiac function, which is an important environmental factor that causes unsafe behavior, and the waste heat loss in the workshop is serious. Taking the heat reservoir power of 10kW as the research object, the role of heat shield under different water flow conditions in the waste heat recovery and reduction of workshop temperature was analyzed. The results show that when the mass flow rate of cooling water is 0.7kg/s, the average indoor temperature is 22.39°C, the cooling range is 39.14%, and the waste heat recovery efficiency is 84.4%, and the heat recovery effect is obvious. At the same time, the fitting relationship between outlet water flow and water temperature is obtained. The research results can provide a reference for the improvement of the thermal environment and waste heat recovery and utilization of the actual high-radiation heat workshop.

Performance analysis of a novel dual exhaust mixed refrigerant heat pump with large temperature lift

The substantial demand for heat energy, ranging from 70 − 100°C in industrial and commercial sectors, presents a significant challenge when utilizing traditional air source heat pumps. The conventional single-stage air source heat pumps often struggle with low system efficiency and poor operating conditions when tasked with heating with large temperature lift. To address these issues, a novel dual exhaust mixed refrigerant heat pump cycle was proposed. By incorporating an intermediate pressure compression stage in parallel, the proposed system can achieve an optimal temperature match in the recuperator, and lead to a significant enhancement in the coefficient of performance (COP). Compared to a single stage mixed refrigerant heat pump cycle, the novel system improves the COP from 5.063 to 5.756, representing an increase of 13.68 %. Concurrently, the exergy loss proportion of the recuperator decreases from 18.8 % to 13.7 %. The proposed system consistently demonstrates superior COP and exergy efficiency regardless of whether the ambient temperature is within the range of 0 °C to 20 °C or the outlet water temperatures between 80 °C to 100 °C are present. These findings provide theoretical guidance for enhancing the performance of high-temperature heat pumps with large temperature lift.

Numerical investigation on thermal performance of three configurations of solar thermal collector integrated with metal hydride

This study investigates the optimal configuration of a Metal Hydride-based Solar Thermal Collector (MH-STC) by developing a transient 3D mathematical model to simulate three distinct configurations: C1, C2, and C3. These configurations differ in the placement of water pipes within the metal hydride bed C1 features pipes in the top region, C2 in the core zone, and C3 at the bottom. The performance of these configurations was rigorously compared based on hydrogen charge state, outlet water temperature, useful energy output, and thermal efficiency across varying water flow rates. Results reveal that configuration C1 achieves superior thermal performance during daytime operation, producing outlet temperatures up to 10 °C higher than the other configurations. Conversely, configuration C3 excels at nighttime heating, delivering water temperatures approximately 11.5 °C higher than C1. Furthermore, the analysis indicates that hydrogen desorption pressure significantly impacts outlet water temperature; for instance, increasing the pressure from 2.41 bar to 6 bar enhances the average outlet temperature of the C3 design by about 20 °C during the day and reduces it by approximately 15 °C at night. These findings highlight the critical need for optimizing solar collector designs to effectively meet the thermal demands of both daytime and nighttime applications.

Experimental study on thermal performance of reverse flow solar collector for dual heating applications

AbstractThe present study investigated the performance of dual function reverse flow solar collector (RFSC). The impact of the mass flow rate of air and water on outlet temperature, thermal performance, and overall performance of dual‐function solar air heater (SAH) has also been investigated. An experimental investigation of three different working models namely, Model‐A: SAH, Model‐B: solar water heater (SWH), and Model‐C: integrated solar air‐water heater (SAWH) for dual heating applications was performed to analyze the actual performance of these models. The investigation of the impact of time intervals on the water inlet and outlet temperatures at various mass flow rates of water is conducted to analyze the time‐varying efficiency of SWH systems. Furthermore, the effect of solar intensity on the performance of the dual‐function heating system has also been explained. The result reveals that the maximum thermal efficiency of Models: A and B can be achieved at about 78.8% and 67.9%, at a mass flow rate of 0.0644 and 0.10 kg/s, respectively, according to the experimental findings. The maximum temperature rise of air and water reaches about 52.4 and 55.58°C for Models A and B, respectively. The total efficiency of Model C reaches 81.69%, exceeding that obtained in Models A and B individually. The efficiency, outlet temperature of the fluid, and heat transfer effectiveness of the system strongly depend on the mass flow rate. The increase in heat removal factor is negligible for a higher flow rate (more than 0.10 kg/s).

Performance optimization for solar photovoltaic thermal system with spiral rectangular absorber using Taguchi method

Solar collector systems efficiently transform sunlight into energy that may be used to meet various needs. This research aimed to use the Taguchi method to determine the ideal operating parameters for a solar thermal collector with a rectangular spiral absorber. Controllable parameters including mass flow rate, solar radiation, and absorber design were manipulated during the energy recovery process, and features like PV temperature and outlet water temperature were used to assess the system’s effectiveness. The findings indicate that certain criteria significantly affect response indicators. The observed percentage contribution of absorber design, solar radiation, and the mass flow rate was 69.19%, 27.99%, and 2.83% in PV surface temperature. In comparison, the individual percentage contributions were 73.63%, 13.51%, and 10.57% for absorber design, solar radiation and mass flow rate for water output temperatures. The present model’s R2 values for PV and outlet water temperatures are 97.24% and 99.67%, respectively. The Predictive regression model was found in fine harmony and the maximum percentage error is limited to 0.68%. The maximum analytical electrical efficiency was observed with a spiral rectangular absorber of 14.57% at the lowest mass flow rate of 0.04 kg/s at the lowest radiation level of 600 W/m2. In comparison, maximum analytical thermal efficiency was observed with a spiral rectangular thermal absorber of 63.56% at the highest flow rate of 0.06 kg/s and the highest solar radiation level of 1000 W/m2. The analytical and experiment findings were in better agreement in this study, with the highest relative error of 7.52%. According to the study’s findings, the rectangular absorber-based PVT system is at its best at a higher mass flow rate to lower PV temperature and boost thermal energy recovery via water. The present research work can be extended for exergy, environmental, and economic feasibility analysis.

Influence of irregular fiber filling on the performance of hollow fiber membrane modules for cold water production

The countercurrent hollow fiber membrane-based evaporative water cooler (MEWC) offers an eco-friendly and compact solution for cold water generation. This study introduces a random sequential addition algorithm to model the real-world irregular fiber filling within the MEWC. Inspired by the honeycomb structure, the developed 3-D numerical model adopts a calculation unit featuring a hexagonal prism comprising multiple fibers. Validation against experimental data reveals an average relative error of 2.81 % concerning outlet water temperature. The effects of fiber filling patterns (regular layout and random layout) on the velocity and temperature fields of the MEWC are investigated. Comparisons of outlet water temperature, cooling efficiency, consumptive electric power ratio, and heat and mass transfer resistance composition between these layouts under various operating conditions are conducted. The results indicate that the random layout fosters severe channeling effect and large flow dead zones, impairing air side heat and moisture transfer. The random layout exhibits over 15.9 % reduction in cooling efficiency and 36.3 % decrease in consumptive electric power ratio compared to the regular layout. Irregular fiber filling leads to a notable 158.6 % increase in air side heat transfer resistance and a 35.9 % rise in mass transfer resistance. Although irregular filling compromises the cooling performance, it demonstrates potential for energy savings under certain conditions. Design schemes should be carefully tailored to meet specific application requirements by considering these trade-offs.

Performance analysis of natural draft power plant cooling tower: Mathematical modeling of cross-flow type, application in capital cities of Iranian provinces

Cooling towers are heat exchangers that reduce the hot water temperature produced by process equipment through heat and mass transfer between water and air stream. This study investigates the performance of cross-flow cooling towers under various geometrical, physical, and environmental conditions. For this purpose, thermodynamic modeling of the cross-flow cooling tower was conducted, and the governing equations were numerically solved using the finite difference method. Unlike previous studies, the effects of water droplet deformation into an elliptical shape during its fall along the cooling tower were also considered. This deformation, which influences the drag coefficient, Reynolds number of the water droplets, droplet surface area, and its cross-section area, along with the incorporation of buoyancy force in the droplet momentum equation, led to an improvement in the results. Consequently, the maximum computational error in this case was reduced to 1.97 %, compared to the scenario where droplet deformation and buoyancy force were neglected. The change in geometrical parameters of the tower in Tehran and Rasht was investigated, revealing that increasing the outlet radius of the tower from 20 m to 22.5 m decreased the outlet water temperature by 1.21 °C and 0.67 °C and increased the thermal efficiency of the tower by 4.94 % and 2.88 % respectively, while increasing the tower height from 100 m to 120 m, only decreased the outlet water temperature by 0.47 °C and 0.26 °C, and increased the thermal efficiency of the tower by 1.89 % and 1.09 % respectively. Additionally, the cooling tower performance was assessed in the centers of different provinces .of Iran. Results showed that with an initial droplet radius of 1 mm and an inlet water temperature of 50 °C, the maximum and minimum temperature reductions occurred in Shahrekord by 20.16 °C and Bandarabbas by 12.37 °C, respectively.

A multiphysics simulator for stope-coupled heat exchanger operation in deep underground mines

The ever-increasing mine depth offers unprecedented opportunities to access high-grade geothermal resources. By pre-installing pipeline systems in mined-out cavities before waste tailings placement, the stope-coupled heat exchanger (SCHE) has drawn growing attention for its superior socio-economic advantages. However, despite the extensive focus on energy efficiency, the system stability during heat production has been typically overlooked. This study therefore introduces a novel high-fidelity simulator for replicating practical SCHE operation. By embedding non-isothermal pipe flow into an evolutive thermo-poromechanics framework for cemented tailings, the outlet water temperature and multiphysics backfill response in diverse production settings are meticulously studied. Our calculations reveal for the first time that circulating chill fluid within mine backfill can substantially alleviate pressure development, suggesting enhanced system stability with heat-exchanger implementation. We also demonstrate that albeit targeting higher-grade geothermal resources, prioritizing cold-season operation, and pre-charging heat exchangers with production delays could spur heat productivity, the companion thermal pressure generation might still impose significant overloading risks. Conversely, while fast circulation would diminish the end-utilization temperature, the rapid heat removal could indeed facilitate superior efficiency and stability performance for the geothermal system. We believe these new findings hold critical implications for better positioning SCHE as a safely sustainable pathway towards hybrid utilization of deep resources.

Energy and exergy analysis of conventional and modified flat-plate solar collector with dual spiral flow tubes: A comparative study

ABSTRACT The most fundamental collectors for water heating are flat plate solar collectors (FPSCs). They are inexpensive, simple to build, and need little maintenance. Conventional FPSCs have relatively low efficiency. More study is needed to increase the efficiency of FPSC by using novel designs. To enhance thermal performance, various strategies have been implemented through design modifications of flow tubes. In this study, dual spiral-shaped flow tubes were constructed instead of the usual FPSCs number of riser tubes and headers and tested with three different mass flow rates (20.9, 29.9, and 42.1 l/h). The optimum instantaneous efficiency achieved is 70.8% at a flow rate of 42.1 l/h, representing a 13.7% improvement in efficiency compared to the conventional collector and lowering the mass flow rate results in an enhanced exergy efficiency of 3.51% at 20.9 l/h. The modified collector achieves its highest instantaneous efficiency when the outlet water temperature is measured at 53.4°C. The modified collector boosts heat transfers by enlarging the water’s surface contact area and prolonging its flow time, resulting in greater heat absorption and significantly improved efficiency. When all other parameters are kept the same as in a conventional design, highly encouraging results in a modified collector have been recorded.

Comparison and regional suitability evaluation of different backfill source heat pumps using TRNSYS

As global energy demand and carbon emissions continues to rise year by year, the use of renewable energy for heating becomes increasingly urgent. This study employs solar and geothermal energy to supply heat to mining facilities. Initially, three distinct heating systems for mining areas were modeled in TRNSYS: the Backfill Source Heat Pump (BSHP), the Solar Assisted Backfill Source Heat Pump (SABSHP), and the Solar Assisted Backfill Source Heat Pump with Seasonal Heat Storage (SABSHP-SHS). Following a decade of simulation, the optimal system was identified through a comparative analysis that encompassed backfill temperature equilibrium, the inlet and outlet water temperatures for buried pipes, Coefficient of Performance (COP), Partial Load Ratio (PLR), and economic factors. Over the 10-year simulation period, the COP and PLR of the SABSHP-SHS system outperformed both the BSHP and SABSHP systems, showing higher energy efficiency and better heat pump performance. To further assess the regional adaptability of the SABSHP-SHS system, simulations were conducted across four regions with diverse climatic profiles: Shijiazhuang, Yan’an, Xining, and Hegang. The analysis focused on heat collection, efficiency, backfill temperature variation, system energy consumption, and the energy efficiency ratio. The findings indicate that Hegang exhibits the highest solar heat collection efficiency at 89.9% during the non-heating season, while Xining achieves a significantly higher heat collection efficiency of 54.1% during the heating season. These results suggest that the SABSHP-SHS system is particularly effective in regions with pronounced seasonal variations, characterized by extended cold winters and brief, intense summers.

Research on Energy-Saving Control Strategies for Single-Effect Absorption Refrigeration Systems

The automatic control device is a critical component of absorption refrigeration systems. Its functional enhancement can reduce operating costs, improve energy efficiency, and ensure long-term stable unit operation. Given that absorption refrigeration systems operate under various dynamic conditions, the rational design of control strategies is particularly important. This study analyzes the influence of changes in the cooling water and heat source water flow rates on the outlet temperature of chilled water in the unit based on the open-loop response characteristics of absorption refrigeration systems. It proposes a dual-loop energy-saving control strategy for single-effect hot water lithium bromide absorption refrigeration systems based on the setpoint comprehensive optimization algorithm. Considering the multiple variables, strong coupling, large inertia, long time delay, and nonlinear characteristics of absorption refrigeration systems, as well as the difficulties in modeling these systems, this study applies a model-free adaptive control algorithm to the system’s control. It derives both SISO and MIMO model-free control algorithms with time-delay components. Through simulations comparing MFAC, improved MFAC, and traditional PID control, the dual-loop energy-saving control strategy is demonstrated to effectively reduce system heat consumption by approximately 20%, decrease power consumption by about 10%, and enhance the system’s SCOP by approximately 19.3%.

Optimal high-pressure correlation for transcritical CO2 cycle in direct expansion solar assisted heat pumps

Heat demand may be met sustainably by a solar-assisted heat pump that CO2 as a refrigerant. This is made possible by the employment of an ecologically benign refrigerant and a renewable energy source that enhances system performance. At the ideal high pressure, the CO2 heat pump running in a transcritical cycle will function at its highest coefficient of performance (COP). In that way, this study aims to present correlations for calculating the optimum high pressure in a CO2 direct expansion solar assisted heat pump (DX-SAHP). In this study a mathematical model for compressor, solar evaporator and gas cooler was developed and validated experimentally. The mean difference between the mathematical model and experimental results are −3.9%. Two new equations are proposed to calculate the optimum high pressure in a CO2 DX-SAHP. The first one considered environment temperature, water outlet temperature and evaporating temperature, which are easy to measure. These facilities the use of correlation to control the heat pump. The second one considered environment temperature, water outlet temperature and solar radiation, which are more suitable for designing CO2 DX-SAHP. A data base with 100 optimum points was used to curve fitting. Another data base with 50 optimum points was used to compare the results obtained from curve fitting and correlations for the optimum high pressure available in the literature. The proposed correlations shown a maximum error lower than 10.2% despite of the correlations available in the literature from which the errors are about 30%.

Analysis of operation regulation on delay time in long-distance heating pipe systems for practical engineering

The distribution area of the district heating network (DHN) is extensive, and there are inherent time delays and thermal losses in the process of heat transfer through heating pipes. The delay in heat transfer within long-distance heating pipes may result in inadequate heat supply to end-users or excessive energy consumption at the heat source. Therefore, this paper presents a quasi-dynamic model for calculating the transmission delay time in the long-distance heating pipeline. And the model is validated through the measured values obtained from a heating pipeline. The influencing factors of delay time are further discussed, including operating parameters, pipe structure parameters and thermal insulator thickness. Additionally, the impact of pipe delay time in practical engineering is analyzed. In practical engineering, the transmission delay time varies when the pipe structural or operational parameters differ, even under the same outdoor temperature change. The change in inlet water temperature and mass flow rate can impact the change rate of outlet water temperature, thereby influencing the delay time. Furthermore, the delay time exhibited an increase with pipe length, diameter, and thermal insulator thickness; however, the effect of thermal insulator thickness on it was minimal. When the inlet water temperature rose or dropped by 5℃, the delay time grew by more 70 % per 1 km pipe length, about 40 % per 100 mm diameter and less 2 % per 100 mm thermal insulator thickness, respectively.

Modeling and operational characteristics analysis of a dual-source synergetic heat pump based on air energy and biomass waste heat

Air source heat pumps have gradually become a widely used heating solution worldwide due to their advantages of high efficiency, energy conservation, and environmental protection. However, air source heat pumps also face some challenges in practical applications, such as unstable heating and performance degradation in low-temperature environments. In order to improve these problems, based on the cascade heat technology, a new type of dual-source synergetic heat pump system is designed using air energy and biomass waste heat dual heat sources. In order to study its performance, a simulation model of the heat pump system was first constructed using distributed-parameter method. In order to verify the effectiveness of the model, an 18-kW heat pump experimental unit was constructed. By comparing the three key parameters of user side outlet water temperature, high-temperature compressor power, and system coefficient of performance (COP), the results show that the maximum error does not exceed 11 %; Secondly, in order to improve the stability and operational efficiency of the system, a three-level control strategy was designed based on considering the coordination of different grade heat sources; Finally, based on the above, the operating characteristics of the heat pump system were investigated through testing under different external input conditions. The research results indicate that by utilizing cascade heating and parallel heat exchange technology, the heat pump system can achieve stable heating even under large fluctuations in external working conditions. At the same time, compared with air source heat pumps, the COP can be improved by 69.7 % in low-temperature environments. The system results not only provide reference for the design and operation of new heat pump systems, but also provide practical and feasible solutions for the problem of decreased heat pump performance in low-temperature environments.

Numerical investigation of the impact of inlet and outlet ports of water jet impingement cooling modules

AbstractThe ever‐growing applications of high‐power chips have driven research efforts to enhance the performance of their active cooling modules. This study proposes a simple tweak of the cooling module's ports for lower thermal resistance. A dual‐inlet single‐outlet (CP2) jet impingement cold plate (JICP), a dual‐inlet dual‐outlet (CP3) JICP, and a single‐inlet dual‐outlet (CP4) JICP were assessed computationally and benchmarked against a single‐inlet single‐outlet JICP (CP1) at the same area ratio (AR) and average diameter (Davg) of inlet and outlet ports. The results show that the pressure losses inflate by up to 4.67 folds when using CP3 with AR = 5/3 and Davg = 3.0 mm. Yet, this design also shows the largest Nusselt number and the lowest outlet water temperature, module body temperature, average temperature of the target surface, and thermal resistance (0.07415 K/W). The thermal resistance is reduced by 34.13% using CP3 at AR = 3/5 and Davg = 6.0 mm. The temperature uniformity index was boosted to 97.5%. These enhancements are attributed to the shorter and symmetric flow path, the shorter residence time of water within the JICP, and the direct heat diffusion by the walls of the lower chamber.

PERFORMANCE OF WATER COOLING FOR RADIATION HEAT FLUX FUEL STORAGE TANK

Full-surface fire on fuel storage tank emits high radiation heat transfer. As a fire protection strategy, the water curtain cooling system is activated to reduce the temperature on the adjacent tank surface. Therefore, the present work predicts and analyses the radiation heat flux and the maximum flame temperature of different types of fuels. Further, this analyses the effect of fuel total mass on radiation heat flux and maximum flame temperature and observes the effect of distance between two tanks on radiation heat flux distribution. The relationship between water cooling flow rate and outlet water temperature that absorbed radiation heat flux has been studied. The study has been conducted by using the Consequence modeling software trial version. The modeling setup of the tank is 17 m in height with 65 m inner diameter, and the meteorological data used are 5.4 m/s wind speed with north wind direction at atmospheric pressure in order to imitate the worst-case fire scenario. The results reveal that the gasoline fuel emitted the highest heat flux value of 11.03 kW/m2 and the raw gasoline sample emits the lowest heat flux value of 9.14 kW/m2. Furthermore, the total mass of the fuel shows no effect on the maximum flame temperature of 958.51°C. According to the findings, the critical tank distancing is 36 m and thus the appropriate tank distancing of 40 m is highly recommended by the standard. The result shows that the water cooling rate of 4.1 lpm/m2 is an excellent practice of water cooling to cool down the temperature of the fuel tank which is exposed to radiation heat flux.

Enhancing thermal efficiency in flat plate solar collectors through internal barrier optimization

This study investigates the impact of introducing horizontal barriers within the internal cavity of flat plate solar collectors on their thermal efficiency. The primary objective is to enhance thermal performance by reducing convective heat loss. An experimental test bench was constructed to evaluate five solar collectors under controlled conditions. One collector was unmodified as a reference, while the other four had 1 to 4 horizontal barriers inserted between the absorber plate and glass cover. Each collector’s efficiency was assessed by measuring inlet and outlet water temperatures, incident solar radiation, ambient temperature, and water flow rate. Efficiency versus heat loss parameter curves were generated, and correction factors were applied to account for material and sensor differences. The collector with four barriers demonstrated the highest overall thermal efficiency, achieving an efficiency improvement of up to 12 % compared to the reference collector. Specifically, the efficiency of the reference collector was around 70 %, while the collector with four barriers reached an efficiency of approximately 82 %. Introducing two barriers resulted in a 9 % increase in efficiency, bringing it to about 79 %. Conversely, the collector with three barriers showed a slight decrease in efficiency to 68 %. The barriers effectively reduced internal convective heat loss, enhancing the collector’s ability to harness incident solar radiation. Inserting horizontal barriers within the internal cavity of flat plate solar collectors significantly improves thermal efficiency by reducing convective heat loss. The optimal configuration, based on this study, involves using four barriers. This method presents a straightforward yet effective approach to enhancing solar collector performance. Future research should focus on refining barrier design and placement for different collector sizes and geometries, potentially supporting broader adoption of solar thermal energy systems and contributing to sustainable energy solutions.

Design of metal foam baffle to enhance the thermal-hydraulic performance of shell and tube heat exchanger

Solid baffles are widely used in shell and tube heat exchanger (STHX), while the highly increased flow resistance and dead zones remain serious drawbacks in the applications. To address this issue, metal foam baffle is proposed in this study to replace solid baffle. The numerical model with considering the thermal non-equilibrium between fluid and foam baffles was established. Laminar flow is assumed in the foam baffles region and the realizable k-ε turbulence model is assumed in the open region. Effects of porosity, pore density, thickness and number of foam baffle (N) on the performance were examined. Results show the foam baffles always lead to lower pressure drop of STHX compared to the solid baffles. Compared to five 2 mm thick solid baffles, five 6 mm thick metal baffles with the porosity of 0.80, 0.85 and 0.90 results higher outlet temperature at the pore density greater than 80, 120 and 160 PPI, respectively. The metal foam baffle leads to higher outlet water temperature compared with solid baffles at the baffle number N ≤ 7. The foam baffles with optimum pore parameters reduced the pressure drop by 12.9 % and increase the outlet and inlet temperature difference by 31.0 % compared to the solid baffles.

Heat transfer analysis of solar distillation system by incorporating nano‐enhanced PCM as thermal energy‐storage system

AbstractThe technology of solar still shows up as an effective and affordable solution to convert available brackish water into potable water. The present study aims to address the challenge of providing freshwater by desalinating brackish water using solar energy. An attempt has been made in this work to make a desalination system for the efficient utilization of solar energy by using a parabolic reflector and energy‐storage material. Modification in the desalination system and storage of energy facilitates the continuation of the process in sunshine and off‐sunshine hours which increases yield output. To investigate the objectives, helical‐shaped focal tubes and nano‐enhanced phase change material (PCM) are prepared. The desalination system is coupled with nano‐enhanced PCM by placing it in the annular space of a helical‐shaped focal tube. The heat transfer coefficient ranged from 11.46 to 28.77 W/(m² K). PCM 3 (i.e., base PCMs with 1.5% nanoadditives) achieved a maximum productivity of 3533.3 mL/m²/day, marking a 97.89% improvement over the system without PCM. The preheated water outlet temperature reached 67.4°C, and the basin water temperature was 75.35°C. The highest concentrator efficiency recorded was 49.82% at a mass flow rate of 0.0053 kg/s. Thermodynamic analysis showed a 67.19% enhancement in overall thermal efficiency with PCM 3 compared with the non‐PCM scenario. Additionally, the system attained a maximum average exergy efficiency of 12.29% and the shortest payback period of 115 days. The study concludes that the base PCM sample with a 1.5% mass concentration of nanoparticles was optimal.

Performance of a Simplified Computational Fluid Dynamics Model for a Phase Change Material–Water Finned Heat Exchanger Under Different Orientations

ABSTRACTThe prevalent numerical models for simulating axially finned heat exchangers with phase change materials (PCMs) and water as the heat transfer fluid rely on computational fluid dynamics (CFD) techniques, with a primary focus on phase change modeling. However, the computational demands of these models, incorporating phase change effects and resolving PCM movement in the liquid state, are substantial. From experiments suggesting that conduction in the solidified PCM around the finned tube dominates heat transfer during the heat discharge process, this article introduces a simplified CFD‐based model in which convective flow of the PCM is neglected. The model is experimentally validated using a 1‐m‐long axially finned heat exchanger prototype with four fins, recording temperatures under different water flow rates and orientations (horizontal and vertical). Results show that the proposed model predicts outlet water temperature satisfactorily, with absolute errors below 1.0°C and 2.2°C for the horizontal and vertical orientations, respectively. Additionally, the model can capture the temperature trend inside the PCM for the horizontal orientation.