Heat Exchange Area Research Articles

Stability analysis and multi-objective optimization of methanol steam reforming for on-line hydrogen production

The potential solution to hydrogen storage and transportation challenges is provided by liquid fuel-based on-line hydrogen production. An online hydrogen production device has been constructed and the stable output of hydrogen at 6.8 bar under dynamic conditions of 6–13 Nm3/h has been achieved. To achieve optimal economic and thermodynamic performances, the mathematical models for mass, energy, and techno-economics are constructed based on field test data. The Non-Dominated Sorting Genetic Algorithm is employed to update temperature splitting points between multi-stage heat exchangers, targeting multi-objective optimization of heat exchange area, system energy efficiency, and annual average cost. Pareto optimal solutions indicate that such optimization can improve system energy efficiency by 0.03%–3.76% and decrease the hydrogen production cost from 0.004 $/kg to 0.599 $/kg. This work demonstrates the feasibility and effectiveness of multi-objective optimization for online hydrogen production system design and offers important guidance for decision-making in heat exchange network schemes.

An advanced closed-loop geothermal system to substantially enhance heat production

Heat production through conventional closed-loop geothermal systems is constrained by the limited contact area for heat exchange between rock formations and the wellbore. To address this challenge, an advanced closed-loop geothermal system (ACGS) is proposed to enhance heat production in this research. The ACGS incorporates a hydraulic fracture, partitioned by a horizontal insulator for vertical zonal isolation of fluid flow in the fracture, into the closed-loop system’s fluid circulation. To assess heat production from the ACGS, a three-dimensional ACGS numerical model is established and validated, utilized to simulate heat production through the ACGS under conditions of different fracture dimensions and structures, tubing materials, and fluid heat capacities. Performances of complicated fracture structures, including a branched fracture and a multiple-wing fracture, in improving heat production are evaluated. It is found that due to the incorporation of a double-wing fracture, the cumulative extracted heat of a closed-loop system over 20 years is enhanced by 162.94 %. Increasing fracture half-length and fracture height both enhances the heat production of the ACGS considerably. Polyurethane foam proves an excellent tubing material for the ACGS due to its low cost and outstanding adiabatic functionality. Compared with a multiple-wing fracture, a branched fracture results in better heat production through the ACGS, with more fracture branches leading to higher heat production. A branched fracture can improve the cumulative extracted heat from a closed-loop system over 20 years by 321.77 %, and increasing the inter-branch angle further enhances heat production. Working fluid with smaller heat capacity yields considerably higher outlet temperature.

A liquid-cooled plate based on bionic flow channels evolved from the shape of leaf veins and tree roots

With the rapid development of lithium-ion (Li-ion) batteries, battery thermal management (BTMS) is increasingly essential for the temperature control of Li-ion batteries. The energy required to control temperature is coming into focus. In order to consume less energy to control temperature and improve temperature uniformity, the liquid-cooled plate (LCP) based on bionic flow channels evolved from the shape of leaf veins and tree roots is proposed. In this BLCP, different from the others BLCPs, it is divided into a reinforced heat exchange area located in the middle and back part of the plate and a normal area located in the front part of the plate. Firstly, 16 sets of orthogonal tests are conducted based on four parameters: the distance of the hexagon from the outlet (a), the distance from the inlet (b), the distance between two adjacent hexagons (c) and the size of the hexagon (d). Secondly, Optimization was investigated based on NSGA-II for two objectives: temperature and pressure drop. The simulation results are analyzed based on the optimized structural parameters (a = 30 mm, b = 8 mm, c = 50 mm and d = 90 mm). After Comparing the optimization results with the simulation results, the temperature and pressure drop errors were 0.56 percent and 3.8 percent, respectively. The effects of flow rate and thickness of the fluid domain on temperature and pressure drop are next discussed separately. Finally, after comparing the optimized bionic liquid cooling plate (BLCP) with the conventional liquid cooling plate (CLCP) based on temperature pressure drop, velocity, and synergy angle, conclusions are made at the same inlet width, height, flow rate, and velocity (V = 0.2 m/s). This leads to the criterion of energy loss becoming only the pressure drop. The BLCP for pressure drop is 14.2 percent lower than the CLCP, which means less energy loss. The maximum temperature of the BLCP is 0.7 °C lower than that of the CLCP. Furthermore, the former has a better ability to suppress the rate of temperature rise and better temperature uniformity. In addition, this proposed new structure and research methods can be applied to the subsequent study of LCP.

Solar air heater energy and exergy enhancement using a v-corrugated wire mesh absorber: An experimental comparison

In this paper, the energy and exergy performance of a double-pass solar air heater (SAH) using a novel model of a v-corrugated wire mesh absorber (CM-SAH) is investigated experimentally. The v-corrugated wires are adjacent to each other in one layer along the airflow direction to reduce the hydraulic resistance. Simultaneously, this arrangement increases the surface absorptance rate of solar radiation and expands the heat exchange area. To evaluate the performance of CM-SAH, a standard SAH having a v-corrugated absorber plate (CP-SAH) and the same configuration dimensions is compared with CM-SAH. The comparison is achieved under the same operating conditions and using different air mass flow rates of (0.01, 0.02, and 0.03 kg/s). The results show that the CM-SAH outperformed the CP-SAH in terms of thermal efficiency, exergy efficiency, and output air temperature. The maximum thermal efficiencies reach 87.3 % and 65.1 %, while the maximum exergy efficiencies reach 4.4 % and 3.4 %, for CM-SAH and CP-SAH, respectively. In addition, the thermal efficiency of CP-SAH decreased after midday while that of CM-SAH continuously increased.

The novel stereoscopic cooling plate designs and performance analysis for battery thermal management systems

This study explores the design and performance of liquid cooling plate-based battery thermal management system for lithium-ion battery packs through numerical simulation. We first assess traditional straight-channel cooling plates with three different placement strategies. The conventional design with bottom-mounted cooling plates demonstrates the most effective thermal management at the same total coolant mass flow rate. This suggests that the influence of reducing coolant flow velocity on the cooling performance outweighs the influence of increasing the heat exchange area under our simulated conditions. Advanced stereoscopic cooling plate structures, referred to as 3DCP-A and 3DCP-B, are then introduced, significantly enhancing battery thermal management performance. To achieve a maximum temperature difference ≤ 5.0 K for the most discharge process, the required mass flow rate of the 3DCP-B decreases by 30.0 g∙s−1 and 10.0 g∙s−1 compared to the conventional bottom-mounted cooling plate and 3DCP-A, respectively, and the pressure drop reduces by 75.9 % and 44.3 %, respectively. The power consumption for the 3DCP-B design is only 6.0 % of that for the traditional design. Finally, the effects of key operating temperatures on the cooling performance of the optimal 3DCP-B design are discussed. The insights obtained in this study provide valuable guidance for developing more efficient and effective pack-level liquid cooling plate-based battery thermal management system, essential for improving the reliability and performance of electric vehicles.

Numerical investigations on the performance of coupled NCL based passive heat removal system of an IPHWR

Passive heat removal systems (PHRS) are indispensable additional safety features in nuclear reactors to deal with station blackout (SBO) conditions. These systems are based on coupled natural circulation loops (C-NCL) connected in series configuration. Further, these system's design, operating conditions, working fluid, heat removal capacity, etc., are specific to the reactor type. In the present work, the operational performance of such first of a kind PHRS of 700 MWe Indian pressurized heavy water reactor (IPHWR) is investigated. For this purpose, a coupled two-phase NCL code is developed, validated and employed. This PHRS consists of two NCLs connected in HHVC-VHVC (horizontal heater and vertical cooler - vertical heater and vertical cooler) configuration. In this study, initially, the full power reactor thermal-hydraulic conditions are established, subsequently, the performance of the PHRS under SBO is investigated. The analyses demonstrated that the system is adequate to effectively eradicate the decay heat by establishing single and two-phase natural circulation (NC) flows of ∼4.5 % and ∼5.6 % of rated conditions in primary and secondary transport loops, respectively. The maximum PHRS capability is predicted to be ∼72 MWth which is more than 3 % of full power. The transients of flow, pressure, energy transfer and heat sink thermal conditions are analyzed when the system changes from forced to NC. Further, the influence of system conditions such as loop diameter, loop height, sink volume, sink temperature and heat exchanger area on PHRS performance was predicted and the changes in system parameters were analyzed. The vital parameters influencing the PHRS performance are identified based on sensitivity analyses. This investigation provides significant insight into the flow and heat transfer characteristics of two-phase and coupled NCLs in the PHRS.

Effect of Heat Exchange Area Margins on Thermal Characteristics of the Heat Exchange System in the Pressurized Water Test Loop during Fuel Assembly Irradiation

The performance of heat exchangers in the pressurized water test loop is a critical factor in ensuring the achievement of irradiation parameters for fuel assemblies and the safety of experimental operations. The effect of the heat exchange area margin on the heat exchangers in the pressurized water test loop for the fuel assembly during the steady-state irradiation is analyzed. Additionally, optimization methods for determining the margin of heat exchange area and corresponding design strategies are further investigated. It shows that the effect of the heat exchange area margin on the heat exchange power is less affected by the inlet temperature of the primary water and is primarily influenced by the flow rate of the primary water. A decrease in the flow rate of the primary water reduces the compensatory effect of the cooling section on power and enhances the weakening effect of the regeneration section on power. Meanwhile, the correspondence between the margin of the regeneration section and the cooling section, established based on design conditions, can be applicable when there are changes in the inlet temperature of the primary water, but it is not suitable when there are changes in the flow rate of the primary water. When the flow rate of the primary water decreases, the cooling section margin required to compensate for the decrease in power caused by the regeneration section margin will increase significantly. In addition, short-circuiting the heat exchange tubes in the regeneration section can effectively enhance the heat transfer capability. Furthermore, setting the heat exchange area margins of the regeneration and cooling sections to zero can serve as a termination condition for iterative calculations in the verification of regenerative heat exchangers under off-design conditions.

Design method for multi-stage fresh air treatment system with high seasonal energy efficiency

Compared to traditional air conditioning systems that only use high-grade chilled/hot water, multi-stage air treatment (MAT) systems use lower grade chilled/hot water and achieve higher energy efficiency. However, the area of heat exchangers in the existing MAT system is designed based on the maximum value of all working conditions, which is large and not appropriate for partial load conditions. Therefore, this study proposes a method for MAT system design wherein the area of heat exchangers can be appropriate for different working conditions. In this study, optimal area ranges for various working conditions in a fresh air system are calculated, and the overlapping range of these optimal area ranges for all working conditions is determined. Then, the performance of the proposed MAT system is numerically calculated, and six different climate zones are selected to evaluate the applicability of the proposed design methods. The results show that: (1) when the system electric power fluctuates within a small range of 3%, the designed area of heat exchangers can vary over a large range of approximately 50% to 150%; (2) compared to the existing MAT system, the designed area of heat exchangers in the proposed MAT system is reduced by 50.0%, and the maximum energy saving rates in the cooling and heating seasons are 10.9% and 9.8%, respectively; (3) in the selected six climate zones, the duration ratio of working conditions where the designed area is not within the optimal range is less than 5%, indicating good applicability of the proposed design method.

Performance analysis and optimization of the Gyroid-type triply periodic minimal surface heat sink incorporated with fin structures

The Triply Periodic Minimal Surface (TPMS) structures demonstrate substantial value and development potential in applications and research concerning heat sinks and heat exchangers. To further enhance the convective heat transfer performance of TPMS, this study proposes a novel method of incorporating fin structures into TPMS. This method is applicable to various types of TPMS, and the new structure constructed using this method is termed “TPMS with Fin Structures (TFS).” Subsequently, a TFS-Gyroid heat sink based on the Gyroid-type TPMS was constructed. This study presents a calculation method for the fin height in TFS-Gyroid (HTFS-Gyroid). Numerical simulation methods were employed to investigate the influence and mechanism of HTFS-Gyroid on the convective heat transfer performance and flow resistance of the TFS-Gyroid heat sink model, with air as the working fluid and under constant wall temperature (100 °C) conditions. The results indicate that within the flow range of 24–120 L/min, as HTFS-Gyroid increases from 0 to 1.6 mm, the average surface convective heat transfer coefficient (h̅) of the TFS-Gyroid heat sink model increases by 27.4 %-34.6 %, and the inlet–outlet pressure drop (ΔP) increases by 42.5–632.8 Pa. As HTFS-Gyroid increases, the PEC of the TFS-Gyroid heat sink model gradually decreases, whereas j/f gradually increases. The primary mechanisms by which the fin structures enhance the convective heat transfer performance of the TFS-Gyroid heat sink are: 1) increased heat exchange area, 2) the fin structures induce a large number of longitudinal vortices and secondary flows within the flow channels, and 3) the formation of “Fins Occupying the Perforated Structure (FOPS)” within the flow channels.

Numerical Investigation of Heat Transfer Intensification Using Lattice Structures in Heat Exchangers

Heat exchangers make it possible to utilize energy efficiently, reducing the cost of energy production or consumption. For example, they can be used to improve the efficiency of gas turbines. Improving the efficiency of a heat exchanger directly affects the efficiency of the device for which it is used. One of the most effective ways to intensify heat exchange in a heat exchanger without a significant increase in mass-dimensional characteristics and changes in the input parameters of the flows is the introduction of turbulators into the heat exchangers. This article investigates the increase in efficiency of heat exchanger apparatuses by introducing turbulent lattice structures manufactured with the use of additive technologies into their design. The study is carried out by numerical modeling of the heat transfer process for two sections of the heat exchanger: with and without the lattice structure inside. It was found that lattice structures intensify the heat exchange by creating vortex flow structures, as well as by increasing the heat exchange area. Thus, the ratio of convection in thermal conductivity increases to 3.03 times. Also in the article, a comparative analysis of the results obtained with the results of heat transfer intensification using classical flow turbulators is carried out. According to the results of the analysis, it was determined that the investigated turbulators are more effective than classical ones, however, the pressure losses in the investigated turbulators are much higher.

Experimental investigation of forced convection heat transfer of heat exchangers with different pin geometries in in-line and staggered design

In this study, the effects of forced convection heat transfer on the surfaces of pin plate heat exchangers with different geometries modified to the heat exchanger form were experimentally investigated. A total of 8 pin fin plate heat exchangers, four of which are staggered and the other four are in-line, were used in the experiments. The heat transfer surface areas of the pin plate heat exchangers are produced equally. The only difference is their geometry, which is produced in four different shapes: triangle, circle, ellipse and square. The experiments were carried out at air velocities of 1 to 6 m/s with 1 m/s increments and at 10 W and 50 W input powers with 10 W increments. The staggered configuration of the pin fin plates demonstrated high performance in heat transfer. The study found that heat exchangers with cornerless pin plates have lower heat transfer compared to those with cornered pin plates. The pressure drops increased as the velocity of the coolant air increased, and the highest-pressure drop was observed in staggered triangular and elliptical pin plate heat exchangers. This research is considered innovative as it involves an experimental comparison between staggered and in-line pin plate heat exchangers in four different geometries, all with equal surface area.

Optimization design analysis on sodium chloride solution evaporative crystallization system driven by high-temperature heat pump

Industrial crystallization is an essential procedure for food, chemistry, and seawater desalination, whereas it accompanies with considerable energy consumption. Although the mechanical vapor recompression serves as an effective tool for heat recovery, it cannot adapt to the lower evaporation temperatures of crystallization process (45–90 °C). To address the above issues, this paper proposed a composited system consisting of high-temperature heat pump and draft tube baffle evaporative crystallizer, which can achieve higher energy efficiency. The coupling mathematical model is solved through the Newton iterative method. The optimized input parameter is determined based on thermal analysis, and the coefficient of performance can reach 5.85. Moreover, the system employs R1234ze as the working medium, achieving the minimum total heat exchange area of 19.27 m2. Simultaneously, this system with different evaporation capacities exhibit similar cycle rates, approximately 58.3. After the system is constructed, the energy-saving and economic evaluation is performed. The result indicates that the system demonstrates an annual carbon dioxide emission reduction about 550 tons, an annual cost reduction of 221,718 CNY, and a dynamic payback period of only 0.89 years, presenting significant economic advantages. By this study, it provides some theoretical guidance for practical engineering applications.

액체 수소 생산을 위한 예냉 시스템의 수소 가스 예냉 온도 및 열 교환기 면적에 관한 연구

액체 수소 생산을 위한 예냉 시스템의 수소 가스 예냉 온도 및 열 교환기 면적에 관한 연구

A heat mining strategy for the potential Enhanced Geothermal System of the Acoculco Caldera Complex, Puebla (Mexico): A numerical approach based on Multiple Interacting Continua

As the world faces a transition to low-carbon electricity, energy markets have witnessed a fast expansion of Variable Renewable Energy, such as solar and wind power. In contrast, the installed capacity of geothermal electricity has increased with at a much lower rate. Continuous innovation is required to maintain geothermal electricity as a cost-competitive technology that helps building flexible power generation systems. Here we propose a heat mining setup for the promissory Enhanced Geothermal System (EGS) of the Acoculco caldera complex, which hosts a heat source in low permeability rocks. The conceptual model of the EGS reservoir consists of a fractured-porous layer between impermeable confining beds. An injection-production triplet is located in line with a fault plane that intersects the model area. Under the assumption of hydraulic stimulation to the fault zone, flow of the injection-production system restricts to a fracture network with secondary and variable permeability. Mass and heat transport is modeled following the Multiple Interacting Continua method with the software TOUGH2. We evaluate the performance of the heat mining system considering water and CO2 as working fluids for a given flow rate. We also evaluate the impact of fracture spacing in the reservoir performance. Results show that for a reservoir temperature of 300 °C, the CO2-based system experiences considerable adverse flow conditions that demands a higher pressure differential between the producer and injector (about 60 bar higher than the water-based reservoir). Likewise, the low heat capacity of CO2 imply a considerable limitation for heat mining. While for the water-based reservoir the cooling front extends throughout the entire reservoir at 30 yr of operation, for CO2 this happens in only about 60%. Additionally, the energy extracted per unit time in the water-based reservoir results more than twice the energy extracted with CO2. Finally, our numerical results show that fracture spacings in the range of 10 to 75 m behave similarly in terms of heat mining performance; decreasing the heat exchange area by increasing the fracture spacing from 10 to 75 m produces a minor impact under the assumption of high permeability fractures. Additional constrains for the fracture network, such as geometry, effective porosity and permeability of both fractures and rock matrix, have to be investigated in future research to better understand the possible performance of the production system.

Study on electric vehicle thermal management system using phase change materials and CO2 heat pump waste heat recovery under cold conditions

The thermal management system plays a pivotal role in electric vehicle. The CO2 heat pump technology, which performs well at low temperatures and environmentally friendly, has emerged as one of the most promising solutions for optimizing the thermal management system of electric vehicles. However, at −30 ℃ to −15 ℃, the CO2 heat pump faces issues with excessively high discharge temperatures and limited Gas Cooler heat exchange area, thereby there is potential of waste heat recovery and utilization. This paper proposes a thermal management system that utilizes PCM heat storage to recover waste heat from the CO2 heat pump. The system aims to insulate the battery during winter parking, reducing the battery’s preheating energy consumption and enhancing the vehicle’s overall energy utilization efficiency. This paper explored the waste heat characteristics of CO2 heat pump under various conditions. Subsequently, Numerical structural optimization analysis of the PCM heat storage was conducted. Finally, an economic analysis of the PCM heat storage is performed, considering the boundary condition of the urban climate. The result showed that Under the heat production control strategy, the PCM heat storage has a high heat storage rate at −30 ∼ -20 ℃ ambient temperature, reaching 1470 W ∼ 2709 W, and the heat storage time is less than 1 h. At −15 ℃, where the energy saving is maximized, the system battery coupled with the PCM heat heat storage consumes only 0.88 kWh for preheating, saving 44 % compared to the 1.58 kWh consumed by the baseline. The PCM heat storage demonstrates a better energy-saving effect in colder areas.

Research on the matching relationship of multi-energy collaborative temperature control in factory farming system based on TRNSYS

In light of the escalating energy crisis and the imperative to address climate change, there exists a pervasive global consensus advocating the reduction of carbon emissions and the exploration of novel energy sources. Despite this consensus, the realm of factory farming continues to rely upon conventional energy sources for heating purposes. This study focuses on the investigation into the multi-energy heating system employed by an aquaculture company in Dalian City. We undertook the optimization of critical parameters within this system and formulate a comprehensive model for the multi-energy system using the TRNSYS transient simulation platform. The optimization process employs the Hooke-Jeeves algorithm, implemented through GenOpt software, with the system annual value cost serving as the objective function. Optimization variables include solar collector area, solar collector slope, thermal storage tank volume, seawater source heat pump power, and wastewater plate heat exchanger area. The findings of this investigation reveal a marked enhancement in the Coefficient of Performance (COP) and overall system performance after optimization. The resultant annual operating cost was $3133.61, indicating a substantial reduction of $1151.86 compared to the pre-optimization period’s cost. The static payback period is determined to be 9.43 years. During the heating period, in contrast to traditional boiler heating, the optimized system manifests a reduction in coal consumption of 4485.03 kg, accompanied by a cumulative decrease in pollutant emissions totaling 11544.46 kg. This substantiates the system’s cumulative economic and environmental viability.

USE OF A TWO-STAGE COMBINED SCHEME FOR HEAT EXCHANGERS CONNECTION IN HEATING POINTS FOR HOT WATER SUPPLY OF INSULATED BUILDINGS

The article addresses the features of the functioning of centralised heat supply systems of residential micro-districts considering the improvement of thermal insulation of existing buildings. It also analyses the performance characteristics of hot water supply heaters installed on individual heat points of insulated buildings. The authors compared the heat transfer surface area of heaters and network water flow rate through the heating point for one-stage and two-stage combined schemes of connection of heat exchangers and heat networks. The analysis of calculation results showed that using a two-stage combined connection scheme reduces the consumption of network water through the individual heat supply unit compared to the one-stage scheme. However, the two-stage scheme causes the necessity to increase the heat transfer surface area compared to the one-stage connection scheme. We generalised the results by formulas for calculating water flow rate from distribution heat networks and heat transfer surface area. It is possible to use the obtained results to develop a strategy for reforming micro-district centralised heating systems. Using a two-stage combined connection scheme for hot water supply heat exchangers installed on individual heating points (IHP) of additionally insulated buildings reduces network water consumption through the individual heating point by 8–16% compared to a one-stage connection scheme. The device of a two-stage combined scheme in comparison with a one-stage scheme causes the increase of heat transfer surface area of heat exchangers of the hot water supply of individual heating points from one and a half to two times depending on the accepted design temperature of heating of cold water at the first stage of the heating unit. The results of calculations are approximated by equations, allowing, with acceptable accuracy, to compare the indicators of two-stage combined and one-stage schemes of connection of water heaters for individual heating points of insulated buildings. Keywords: centralised heat supply, individual heating point, water heaters, hot water supply.

Large-scale physical simulation of injection and production of hot dry rock in Gonghe Basin, Qinghai Province, China

Based on the independently developed true triaxial multi-physical field large-scale physical simulation system of in-situ injection and production, we conducted physical simulation of long-term multi-well injection and production in the hot dry rocks of the Gonghe Basin, Qinghai Province, NW China. Through multi-well connectivity experiments, the spatial distribution characteristics of the natural fracture system in the rock samples and the connectivity between fracture and wellbore were clarified. The injection and production wells were selected to conduct the experiments, namely one injection well and two production wells, one injection well and one production well. The variation of several physical parameters in the production well was analyzed, such as flow rate, temperature, heat recovery rate and fluid recovery. The results show that under the combination of thermal shock and injection pressure, the fracture conductivity was enhanced, and the production temperature showed a downward trend. The larger the flow rate, the faster the decrease. When the local closed area of the fracture was gradually activated, new heat transfer areas were generated, resulting in a lower rate of increase or decrease in the mining temperature. The heat recovery rate was mainly controlled by the extraction flow rate and the temperature difference between injection and production fluid. As the conductivity of the leak-off channel increased, the fluid recovery of the production well rapidly decreased. The influence mechanisms of dominant channels and fluid leak-off on thermal recovery performance are different. The former limits the heat exchange area, while the latter affects the flow rate of the produced fluid. Both of them are important factors affecting the long-term and efficient development of hot dry rock.

Optimization study of the circuitry for 5 mm small-diameter finned-tube heat exchanger in air-source heat pumps

Finned-tube heat exchangers (FTHXs) are currently extensively utilized in residential air-source heat pumps (ASHPs), but their escalating costs pose an urgent issue needing resolution. This study investigated the feasibility of replacing the 7 mm diameter FTHX in the outdoor unit of an ASHP with a 5 mm small-diameter FTHX, aiming to reduce material consumption without compromising performance. Based on the Intelligent System for Heat Exchanger Design (ISHED), a 6–3-1 circuitry (6 circuitries merging into 3 then 1) optimization scheme tailored for the 5 mm diameter FTHX was proposed under non-uniform airflow distribution. The performance differences between this circuitry and the baseline were then analyzed through numerical simulations. Finally, comparative tests were performed between the original FTHX and the modified 5 mm diameter FTHX. Overall, even with a 5.10 % reduction in total heat exchange area, its heat exchange capacity and efficiency still meet the performance standards for the initial ASHP. Notably, the proposed 5 mm diameter FTHX reduces the material costs and refrigerant charge by 19.76 % and 12.28 %, respectively. This phenomenon illustrates the considerable economic benefits of reducing the volume of FTHX. Additionally, it holds significant practical value in promoting the use of natural refrigerants including hydrocarbons according to the new international legislative framework.

Physically based heat exchanger sizing method for the thermal management system of all-electric regional aircraft

Fully electric propulsion systems integrating hydrogen-powered fuel cells and batteries are promising options to reduce the overall climate impact of regional aircraft. However, the increase in low-temperature heat sources aboard the aircraft calls for advanced thermal management system solutions. To address this challenge, this study presents a sizing methodology for ram air heat exchangers in the nacelle-integrated cooling loop of an all-electric regional aircraft based on the ATR-72 platform. Different discretization schemes are compared to identify an optimal sizing method. The results highlight the simplicity and efficiency of the 0D ε-NTU model. Geometric design variables are optimized with respect to drag and mass during a hot-day take-off. The resulting Pareto front reveals a tendency for low airflow outlet temperatures and large diffuser area ratios to result in lightweight designs but in turn, induce high drag and require a large installation space. Comparative analyses of specific optimal ram air duct designs and equivalent skin heat exchangers demonstrate the potential of a second heat sink over a flight mission. The limited heat transfer area of the skin heat exchanger proves insufficient for hot-day take-off and climb but offers advantages during cruise and descent thanks to the reduced drag.