Improvement In Thermal Performance Research Articles

Effect of single and multiple protrusions on thermal performance of slot jet impingement with curved surface

The current study uses numerical methods to evaluate the thermal and flow characteristics of air jet impinging on concave surfaces with single and multiple protrusions on a surface. The impact of different operating parameters is also studied, including Reynolds number, jet inclination angle and nozzle-to-plate distance (H/B). No significant improvement in the overall thermal performance is noted with a single protrusion on the surface, although a higher heat transfer is observed in the stagnation zone. On the other side, the multiple protrusions on the surface have shown an increase or decrease in the overall thermal performance of jet impingement depending on protrusion diameter and height. The maximum improvement in the overall Nu is noted up to 19 % for the multi-protruded surface at H/B = 6 with orthogonal jet impingement. An oblique jet decreased the overall thermal performance compared to the orthogonal jet, regardless of the jet inclination angle.

Thermodynamic assessment and optimization on louver fin with non-uniform arrangement at different tube rows by desirability approach

The parametric study explores the thermodynamic performance of louver fin with non-uniform arrangement at different tube rows based on three factors: Reynolds number (Re), number of slotted at first tube row (Ns1), and number of slotted at second tube row (Ns2). The distributions of local entropy generation are displayed and analyzed in detail. Thermal entropy generation is mainly concentrated in the first row, but the viscous entropy generation of the first row is roughly the same to the second row. Compared with plate fin, the louver fins can effectively reduce thermal entropy generation, but also bring greater viscous entropy generation at variable Re. The thermal entropy generation and viscous entropy generation increase, but the thermal entropy generation per unit mass flow decreases and the viscous entropy generation per unit mass flow increases as the increasing Re. It is found that the increase in Ns1 will lead to a far greater improvement in thermal performance than the increase in Ns2. However, the increase in resistance caused by the increase in Ns1 is approximately equal to the increase in resistance caused by the increase in Ns2. Meanwhile, the correlations of the thermal performance and resistance are given, which facilitates the design of the heat exchanger. The non-uniform arrangement is quantitatively optimized using the desirability approach, and the arrangement of first-dense-then-sparse at Re = 900, Ns1 = 8, Ns2 = 4 is given. The arrangement of first-dense-then-sparse can reduce the resistance without reducing the thermal performance evidently.

Experimental investigation on indoor thermal environment improvement and energy-saving of electrochromic window under Singapore's tropical climate

This study aims at analyzing the thermal performance improvement of a gray tintable electrochromic window (EC window) under Singapore's tropical climate. Two climate chambers were experimentally studied, one with a double-glazed EC window and another with a single-glazing window, the most common in the considered region, as the reference. The indoor thermal environment and air conditioning energy consumption were compared respectively to investigate the thermal performance improvement of the EC window. The results, under the sunny outdoor weather condition, showed that the EC window could achieve an interior surface temperature reduction of 4.4 °C under the tinted state and 3.0 °C under the clear state, compared to the reference window. Moreover, the bleached EC window achieved up to 37% improvement in peak Predicted Mean Vote (PMV) over the reference window, while the fully tinted EC window achieved a 50% improvement in peak PMV. Finally, the EC window under the fully tinted state could achieve up to 19% energy savings compared to the reference window. Using the EC window under Singapore's tropical climate can improve the occupant thermal comfort during the daytime and reduce air conditioning energy consumption.

Effect of wellbore layout and varying flow rate on fluid flow and heat transfer of deep geothermal mining system

Optimal wellbore layout and fluid flow supplying scheme are crucial in thermal breakthrough alleviation and performance improvement for geothermal energy recovery. This study aims to evaluate the effect of wellbore layout and fluid flow injection scheme on heat extraction performance and determine the optimal scheme for a sCO2-based deep geothermal mining system. A three-dimensional numerical model is established and the fluid flow and heat transfer characteristics for six types of wellbore layouts is comparatively analyzed. Then the system performance under increasing and decreasing type of varying flow injection scheme is evaluated. The results show that the wellbore layout has great impact on the sufficient degree of heat exchange between the cold working fluid and the hot rock. The triplet triangle layout is superior to the other kinds of wellbore layouts in heat transfer and gives moderate pressure loss. Quintuplet and doublet diagonal layouts give moderate performance, while doublet center straight-line has slightly poorer heat transfer performance than these two layouts. The triplet center straight-line and triplet diagonal layouts provide the two worst wellbore layouts with obvious dead zone visualized in system temperature contour. Besides, the injection flow rate needs to be supplied into the reservoir cautiously. Too large mass flow rate makes too fast heat extraction, and the thermal breakthrough time is shortened and temperature drops dramatically. Moreover, the increasing type of varying flow rate scheme can extend thermal breakthrough time by 50% and significantly raise reservoir outlet temperature, while the decreasing type of varying flow rate scheme deteriorate the system heat transfer performance due to excessive heat extraction in early operation period. Overall, the triplet triangle layout combined with increasing type of varying flow rate scheme can improve the heat extraction performance, enabling a more stable and sustainable geothermal mining system.

Combined numerical approach for the evaluation of the energy efficiency and economic investment of building external insulation technologies

The objective of this paper is to examine the energy efficiency and economic feasibility of different coating technologies used to improve the thermal insulation of external walls in buildings. The comparison is made between traditional coat insulation and ventilated façade, evaluating their impact on energy consumption to maintain a constant indoor temperature throughout the year by means of a combined numerical approach. . Furthermore, the paper investigates the effect of opening and closing the air gap in ventilated façades on thermal insulation during the winter and summer seasons. Energy efficiency calculations are employed to estimate the economic investment required for implementing the different insulation solutions.The paper proposes an innovative combined approach to determine the performance of the building insulation technologies. Firstly, a computational fluid dynamics (CFD) simulation is carried out on the full three-dimensional geometry of the building during two reference days representing extreme temperature and sun radiation conditions during the summer and winter. This modeling includes the effects of solar radiative heat transfer during the day: for a chosen date, time, and geographical location, the model computes sun altitude and azimuthal angles, along with the corresponding direct and diffuse solar fluxes. In addition, the model uses a multiband thermal radiation approach to capture the different nature of radiative heat exchange according to the light wavelengths. The total heat transfer coefficient of the building walls in each scenario is calculated through the computational fluid dynamic analysis and implemented in an in-house developed library based on the open source Open-Modelica platform to simulate the energy requirement of the building throughout the year. This combined numerical approach provides a comprehensive performance analysis of the studied technologies in terms of electric energy and fuel consumption required for maintaining a constant indoor temperature and internal ambient comfort.The results of the simulations demonstrate that by adopting the two proposed solutions, there was a potential to save approximately 37% of the fuel required for the heating system and more than 51% of electric energy required for the air conditioning systems. Finally, the payback period for each scenario is calculated, and it was found that coat insulation offers the best balance between thermal performance improvement and economic effort, with a payback time close to 20 years.

Evaporation temperature prediction of a direct-expansion solar-assisted heat pump

As known, evaporation temperature is critical for the thermal performance of a direct-expansion solar-assisted heat pump (DX-SAHP), which is subjected to environmental parameters. It is significant to explore the effect of environmental parameters on evaporation temperature and system performance for the optimal design of DX-SAHP systems. An experimental study on the affecting factors of evaporation temperature in DX-SAHP is firstly implemented, and an evaporation temperature prediction model is constructed by multiple linear regression method and validated, which uses solar radiation, ambient temperature and wind speed as independent variables. Based on this, the effect of environmental parameters on evaporation temperature is compared and analyzed. Results show that evaporation temperature is most affected by solar radiation, followed by ambient temperature and wind speed. The weights of solar radiation, ambient temperature and wind speed are 47.6 %, 43.1 % and 9.3 %, respectively. Furthermore, evaporation temperature will have a 1.80, 0.58 and 0.94 °C increase for a 100 W·m−2 increase in solar radiation, a 1 °C increase in ambient temperature and a 1 m·s−1 increase in wind speed, respectively. The prediction model obtains satisfactory accuracy under different conditions and would be helpful for optimal design and thermal performance improvement of DX-SAHP systems.

Convective Heat Transfer and Entropy Generation for Nano-Jet Impingement Cooling of a Moving Hot Surface under the Effects of Multiple Rotating Cylinders and Magnetic Field

In this study, confined slot nano-jet impingement cooling of a hot moving surface is investigated under the combined utilization multiple rotating cylinders and magnetic field. Both convective heat transfer and entropy generation analysis are conducted using a finite element method. Parametric variation of the rotational Reynolds number (Rew between −500 and 500), velocity ratio (VR between 0 and 0.25), Hartmann number (Ha between 0 and 20) and the horizontal location of cylinders (Mx between −8 and 8) are considered. Rotation of the cylinders generally resulted in the degradation of cooling performance while increasing the wall velocity, and the horizontal location of the cylinder was found to positively contribute to this. Heat transfer rate reductions of 20% and 12.5% are obtained using rotations at the highest Rew for the case of stationary (VR = 0) and moving wall (VR = 0.25). When magnetic field at the highest strength is imposed in the rotating cylinder case, the cooling performance is increased by about 18.6%, while it is reduced by about 28% for the non-rotating cylinder case. The hot wall movement contributes, by about 14%, to the overall cooling performance enhancement. Away from the inlet location of the rotating cylinders, thermal performance improvement of 12% is obtained. The entropy generation rises with higher hot wall velocity and higher horizontal distances of the rotating cylinders, while it is reduced with a higher magnetic field for non-rotating cylinders. The best configurations in terms of cooling performance provide 8.7% and 34.2% enhancements for non-rotating and rotating cylinders compared with the reference case of (Rew, VR, Ha, Mx) = (0, 0, 0, 0), while entropy generation becomes 1% and 15% higher.

Influence of spinning flower structure inserts in the thermal performance of LS-2 model of parabolic trough collector with ternary hybrid nanofluid

Parabolic solar trough collector is the most widely accepted technology to use inexhaustible energy. Present research work proposed LS-2 model of parabolic trough collector with various spinning flower inserts and three particles based nanofluid as a heat-carrying medium. Main intention of this examination is to lower the temperature gradient in fluid flow and provide uniform distribution of heat flux on the receiver's outermost surface. A total of ten cases of PTC are examined in ANSYS 22 Fluent. Nine steady receivers are equipped with spinning flower inserts and one without inserts. Hybrid nanofluids with 1% vol. content are attained by blending aluminum oxide, copper oxide, and graphene oxide with water as base fluid. This evolution focuses on the consideration of spinning inserts in the receiver with a range of speed from 0 to 15 rad/s. The flow rate is from 0.016 kg/s - 0.033 kg/s respectively. Highest enhancement for thermal efficiency and heat transfer coefficient are 30.87% and 98.34% for case-9 at 15 rad/s inserts speed than receiver without inserts using nanofluid-6 at 0.033 kg/s. Under the same condition, the highest increment for the pump work requirement is 21.29% for case-9 than receiver without inserts. This means increment of pump work is insignificant than thermal performance improvements.

Experimental study of thermal performance improvement in a cross‐flow heat exchanger by using copper foam

AbstractIn this study, copper foam was used as a porous medium in place of traditional aluminum fins. A comparison between the two heat exchangers—one with fins and the other with copper foam—was conducted under various conditions. The air inlet velocity ranged from 0.9 to 9.3 m/s, and the water inlet temperature ranged from 10°C to 18°C. Different water flow rates were tested. A comparison was made between the performance of copper foam and aluminum fins by calculating several parameters, including thermal resistance, heat exchanger effectiveness, Colburn factor, Nusselt number, friction factor, and area goodness factor (AG). The experimental results showed that at low air velocities, the heat transfer coefficient for both types of heat exchangers was almost equal. However, at high air velocities, the copper foam exhibited a higher heat transfer coefficient. The Colburn factor was higher for the heat exchanger with copper foam than in the conventional fins, where it was equal to 0.1959 for the copper foam and 0.1186 for the fins. On the other hand, the AG was higher in the case of fins than in the heat exchanger with copper foam.

Thermal performance improvement of a LS-2 parabolic trough solar collector using porous disks

This study presents a thorough numerical investigation of a LS-2 parabolic trough collector (PTC) to introduce a manufacturable structure with high performance. This is done by considering all influential parameters such as possible design shapes (full, upward half, and downward half), diameters, spacings, and PPI (pores per inch) of porous materials along with thermal and fluidic features of heat transfer fluid used inside the absorber pipe. It is found that the full-disk cases perform better than half-disk options. Moreover, the thermal efficiency of PTC improves by increasing PPI and the diameter of porous disks, as well as by reducing the space gaps between the disks. Studying the effects of volumetric flow rate and inlet flow temperature shows that the thermal efficiency diminishes by increasing inlet temperature and decreasing flow rate. In addition, the variations of Nusselt number and friction factor for all mentioned parameters are studied, and performance evaluation criteria are developed to assess the simultaneous effects of enhancing heat transfer against increasing the pumping power.

3D printed concrete blocks made with sustainable recycled material

The use of recovered materials in building construction is one of the most effective strategies for reducing the environmental impacts of the construction sector. Innovative technologies such as 3D construction printing can be applied in combination with recycling strategies in order to optimise their performances also from an environmental point of view. In fact, several studies have proposed the processing of waste material into printable material. At the same time, performance studies must be conducted on the building components produced by these methods. This study proposes a methodological approach to design a 3D printable building component made with recycled materials considering the improvement of thermal performances. In particular, the approach is based on three steps: reuse strategy conception; target performance definition, modelling and iterative simulation; 3D printing setting. The methodological approach has been applied to a 3D printable block using as printable material a cement-based mortar with recycled aggregates and recycled insulating material. As a result, the component’s shape (interlocking and inspired by honeycombs) can be customised to achieve the required thermal performance by using recycled materials in the printing process.

Improvement of thermal performance and energy efficiency of micro-thermophotovoltaic with the dual-inlet combustor at appropriate equivalence ratio

Micro-thermophotovoltaic is facing challenge caused by small size, large area-volume proportion and heat loss ratio, reducing the burning stability and output power. So, the dual-inlet combustors with exit-step and porous medium are proposed for micro-thermophotovoltaic system. Effects of equivalence ratio, exit-step and porous medium setting on combustion characteristic and thermal performance are conducted and analyzed. Results demonstrate that 1% air in the second-inlet is conducive to releasing heat of combustion and optimizing wall temperature distribution, where the total equivalence ratio of H2/air keeps 1.0. Furthermore, the exit-step with applicable length and channel height can generate heat recirculation and enhance working performance of micro-combustor, while the employment of porous medium can further enhance heat transmission of gas-wall and boost the radiation temperature Tw. Combustor CP13 with porosity ε = 0.85 obtains the highest average Tw of 1273.9 K at mf = 3.376 × 10-5 kg/s. With the increase of mf, system efficiency of the combustor with porous medium is increased, while that with exit-step reaches the maximum at mf = 4.501 × 10-5 kg/s. The highest output electrical power and efficiency are appeared in combustor CP15 with ε = 0.95 at mf = 5.626 × 10-5 kg/s, that is, 4.2 W and 2.2%.

Numerical Evaluation of Novel Curved Rib Turbulators for Thermal Performance Improvement in Circular Geometries

Internal heating/cooling using roughness elements such as ribs are a promising passive heat-transfer enhancement technique for many thermal applications. The curved ribs are roughness elements that boost the fluid residence time and enhance the thermal-hydraulic performance of the system. In the present study, curved ribs of different cross-sections were fitted at the inner wall of the circular tube to intensify convection heat transfer to the fluid flowing through it. Novel curved ribs of inline configurations of different shapes and geometrical parameters were numerically studied for convection heat transfer using a three-dimensional computational model. The finite volume method discretizes the tube fluid flow domain’s mass, momentum, and energy equations. The local heat transfer enhancement over the tube surface is 2.75 times the smooth tube flow, with Reynolds numbers ranging from 10,000 to 50,000. The cost-effectiveness of this heat transfer enhancement method was quantified using a thermohydraulic performance evaluation factor. This factor accounts for the increased heat transfer at the same pumping power and the same available surface area for heat dissipation. The average heat transfer enhancement at the same Reynolds number and pumping power was found to be 120% to 450% and 98% to 260% of the smooth tube flow.

Improved heating floor thermal performance by adding PCM microcapsules enhanced by single and hybrid nanoparticles

AbstractA heating floor is a low‐temperature emitter consisting of pipelines in which a fluid circulates between 35°C and 45°C. To ensure energy efficiency, occupant comfort, and building material durability, proper heat management is crucial in buildings. By using phase change materials (PCMs) in building envelopes, the indoor temperature can be regulated through the storage and release of thermal energy, which reduces energy consumption and enhances occupant comfort. In this study, we evaluated numerically a heating floor that incorporates a PCM enhanced by nanoparticles (NePCM). The aim of the numerical analysis is to assess the impact of the addition of single and hybrid nanoparticles in different proportions to the PCM layer on the thermal performance of the PCM‐based floor. Therefore, two main objectives are defined. The primary is to take advantage of the storage capacity of a PCM layer by integrating it into the ground; second, to evaluate the hot water temperature levels effect on the floor's performance. Additionally, we address the low thermal conductivity of PCM by enhancing PCM microcapsules with single and hybrid nanoparticles and comparing them to pure PCM. The numerical results obtained show that positioning the PCM microcapsules above the heating tubes (upper position) provides an optimum improvement in thermal performance. Moreover, the addition of hybrid nanoparticles within the base PCM, 1% of Cu mixed with 4% of Al2O3, allows an increase of 4°C, which relates to a reduction of 18% in the internal temperature amplitude and a phase shift of 6 h 30 min compared with the conventional heated floor in which there is no PCM.

Mitigation of hot-spot effect via back side cooling techniques: A potential for electrical and thermal performance improvement

Hot-spot mitigation is an ever-present issue in photovoltaic system and it significantly affects the performance of photovoltaic (PV) panels. Most of the hot-spots are actually partial hot-spots which cover only a part of PV cell, or part of PV panel. In this work an influence of cooling mechanism on hot-spot mitigation is investigated by using previously developed numerical model. Specific parameters such as insolation, hot-spot intensity, convection intensity, cooling medium temperature and number of affected cells were varied for single panel. By varying parameters, it was found that partial hot-spots with less than 15% shade percentage on up to 4 cells (corresponds with 1% of total shade on PV panel) can be mitigated with adequate cooling technique applied on the PV panel. The hot-spot cases with larger shade can be mitigated, but only with high cooling intensity which makes the feasibility of the mitigation highly questionable. Hot-spot cases with more than 15% shade percentage on more than 10 affected cells (corresponds with 2.5% of total shade on PV panel) practically cannot be completely mitigated with any back side cooling technique. Nevertheless, cooling technique still provides additional electrical energy gain even with intense hot-spot cases. Results gained in this investigation can also be used to estimate potential in higher electricity output with specific cooling technique, and to estimate thermal energy potential such as house or hot water heating. A simplified case study is presented, where result application is explained step-by-step. These results are of particular interest for PV panels installed in urban areas with lots of obstructions and where regular cleaning is not practical. Such applications are rooftop PV systems, facade PV and photovoltaic-thermal (PVT) systems.

Numerical investigation on the thermal performance of parabolic trough solar collector with synthetic oil/Cu nanofluids

Nanofluids as the advanced heat transfer fluids, could be used in the parabolic trough solar collector system because of the enhanced thermal transport properties. In this paper, the effects of the same nanoparticles with two different base fluids on the thermal performance of the collector are numerically investigated by finite element method. Moreover, the effect of nanofluids on the cross-sectional temperature distribution of the absorber tube, which is well-known to affect the collector performance is here investigated. The numerical study is divided into two groups according to the value range of inlet velocity and inlet temperature, which represents different application scenarios of the collector. The results show that the synthetic oil/Cu nanofluids could increase the convective heat transfer coefficient under wide working conditions, but more pumping work is required because of the increase in pressure drop. The cross-sectional temperature difference of the absorber tube is greatly decreased with synthetic oil/Cu nanofluids. Furthermore, it’s found that Cu nanoparticles could trigger thermal and exergetic efficiency increment, especially at a low flow rate and high working temperature. The thermal performance improvement of these two thermal oils by Cu nanoparticles is different, and Syltherm 800 is more suitable for being the base fluid of nanofluid.

A Novel Heat Treatment Strategy Based on Quenching and Carbides Preprecipitation and Subsequent Critical Quenching to Improve the Thermal Fatigue Performance of AISI H13 Tool Steel

The effects of conventional quenching and based on quenching and carbides preprecipitation and subsequent critical quenching (QPQ) processes on the microstructure evolution, thermal stability and thermal fatigue are studied for H13 tool steel. The results show that the QPQ treatment is beneficial to precipitate smaller and more uniformly distributed carbides during the tempering. According to the analysis of microstructure and mechanical properties, it is found that the tempering after QPQ treatment can refine the grain size of the steel by about 60% and can increase the impact toughness by 34.8%. Moreover, it is also found that the activation energy required by the QPQ treatment is higher than that of the conventional quenched samples for long‐time tempering, which is mainly related to the coarsening and accumulation of carbides. According to the statistical analysis results of average thermal fatigue crack length, crack density, and surface hardness, the improvement of thermal fatigue performance of the QPQ treatment after tempering is mainly attributed to the uniform fine carbide and grain refinement, which passivates the crack tip and improves the service life to a certain extent.

Thermal performance assessment by using a wavy porous obstacle in a circular vented cavity under non-uniform magnetic field during forced convection of hybrid nanofluids

In this study, effects of using a wavy porous object on the thermal performance improvement in circular vented cavity are numerically assessed during hybrid nanofluid convection under non-uniform magnetic field. Numerical analysis is conducted for varying values of Reynolds number (Re, between 200 and 1000), Hartmann number (Ha between 0 and 50), magnetic field inclination (γ between 0 and 90) while Darcy number is taken between and . The amplitude is considered between 0 and 0.5 while wave number of the corrugated porous object is taken between 2 and 16. Significant impacts of the porous object parameters and permeability on the flow pattern distribution and thermal performance improvements are obtained. The magnetic field improves the heat transfer for the lower permeability object case at Ha = 10 while the average Nusselt number (Nu) is reduced for the case with higher permeability object case. Average Nu number improvement up to 33.5 is obtained with the imposed non-uniform magnetic field effects. Average Nu variations of 27.3 and 15 are obtained when the corrugation wave number and amplitude are varied. The Constrained Optimization BY Linear Approximations optimization is used to achieve the highest thermal performance of the configurations.

Overlapping grid SQLM for third-grade modified nanofluid flow deformed by porous stretchable/shrinkable Riga plate

Abstract The improvement in thermal performance of fluid and the control of energy loss are equitably significant. Therefore, the purpose of this study is to analyze entropy generation, stagnation point flow, and thermal characteristics of non-Newtonian third-grade modified hybrid nanofluid generated by a stretchable/shrinkable Riga plate in a porous medium with varying flow viscosity. In this analysis, a modification of hybrid nanofluid is considered by using pure water as a base fluid and three various nanomaterials (aluminium oxide, copper, and nickel) as nanoparticles in the characterization of heat transfer. Furthermore, the contribution of heat source/sink and viscous dissipation are accounted for in the model. The suited transformations are enforced to remodel the governing mathematical equations to produce ordinary differential equations that are conveniently tackled via spectral quasilinearization method (SQLM) along with the overlapping grid idea to yield numerical solutions. The preference of this approach over others has been justified through discussion of error bound theorems, residual and solution errors, computational time, and conditioning of matrices. The physical significance of disparate governing parameters on flow variables, velocity gradient, thermal rate, and entropy generation are scrutinized through graphs and tables. Crucial findings of the study include that temperature of the modified hybrid nanofluid enhances quickly (better thermal conductor) than temperature of single nanofluid, hybrid nanofluid, and conventional third-grade fluid for higher Biot number, variable viscosity, and heat source parameters. Mass suction enhances fluid flow and physical quantities of interest, but suppresses the fluid temperature. An increase in variable fluid viscosity, modified Hartmann number, and third-grade parameters enhances the wall drag coefficient while lowering the rate of heat transfer, and the opposite is true for porous media. More entropy is generated in the system by high variable fluid viscosity, suction, viscous dissipation, modified Hartman number, and non-Newtonian parameters. Owing to high velocity and temperature associated with modified hybrid nanoparticles, modified hybrid technology is recommended in enhancing the physical attributes of the fluid with minimal cost effects. In engineering and industrial point of view, this study can contribute significantly in thermal improvement of the working fluid.

Comparative study of novel backfill coupled heat exchangers using different waste materials in underground stopes

Underground mines in China are rich in geothermal resources. Based on backfill mining technology, the collaborative development of deep mineral resources and geothermal resources can be realized. The key of this approach is to form artificial thermal reservoirs by heat storage backfill body and to extract geothermal energy as much as possible through the built-in pipe. It is important to investigate the backfill material and system parameter design to improve the heat storage and release performance of backfill body and enhance the extraction efficiency of geothermal energy in mine. In this paper, experimental and simulation studies of backfill coupled heat exchanger system with different backfill materials are carried out to make a comparative study. The backfill materials involved include traditional backfill material, natural flake graphite backfill material and paraffin RT28 backfill material. After comparing the heat storage and heat release behavior, liquid fraction variation and efficiency of different systems, the natural flake graphite backfill body which has better engineering value is selected to further conduct experiments to study the influence of surrounding rock temperature, initial temperature of backfill body and inlet water temperature on the thermal performance of the system. The results show that with the increase of surrounding rock temperature, initial temperature of backfill body, or the decrease of inlet water temperature, the total heat storage, heat release and energy utilization coefficient of the system all increase. When the initial temperature of backfill is 26 °C, surrounding rock temperature is 45 °C, inlet velocity and temperature are respectively 0.7 m/s and 18 °C, the energy utilization coefficient of the system is the highest, which is 81.4%. The research results are helpful to the design of heat storage backfill body and the improvement of thermal performance of the system.