Maximum Heat Research Articles

Computational investigation of transportation and thermal characteristics in a bi-modal slurry flow through a horizontally placed pipe bend

In this study, we develop a three-dimensional computational model to explore the transportation and thermal characteristics of a bi-modal slurry flowing through a horizontally placed 90° pipe bend. The slurry comprises silica sand (SS) and fly ash (FA) granular, with varying combinations (65:35, 75:25, 85:15, 95:05, and 100:0). The computational investigation has been carried out for different carrier fluid's characteristics, including Prandtl number, and flow velocity (5 m/s), for efflux concentrations of Cw = 40–60% for each mixture. Validated with experimental data, the computational approach employs a two-phase Eulerian-Eulerian RNG k-ε turbulence model and the kinetic theory of granular flow. Results reveal that the 65:35 combination exhibits minimal pressure drop, and the 100:0 combination shows maximum heat transfer characteristics, particularly with low-viscosity fluid (Pr = 2.88) and high particle efflux concentration (Cw = 60%). The study also examines bend loss coefficients (Kt), concentration distribution, convective heat transfer coefficient (h), and Nusselt number (Nu) across different Prandtl fluids and efflux concentrations.

Numerical simulations on loss of ICRF-heated NBI ions in EAST

The loss of ion cyclotron resonance frequencies (ICRF)-heated neutral beam injection ions in experimental advanced superconducting tokamak was numerically investigated by ORBIT code simulations. The effects of collisions and ripples on particle losses were taken into account, and the distributions of fast ions generated by different beams in combination with ICRF heating were calculated using the TRANSP code. Results showed that ICRF waves altered the orbital distributions of beam ions, causing an increase in trapped ions and fast ion losses. Additionally, for co-current injected beams, perpendicular injection resulted in higher fast ion losses in synergistic heating than tangential injection. The study also found that the synergistic effect of collisions and ripples enhanced fast ion losses, which were highly localized and generated a maximum heat load of 0.165 MW m−2 on the first wall. However, conducting synergy heating experiments at high plasma currents and low effective ion charge numbers can significantly reduce the loss of fast ions.

Combustion characteristics of RP-3 aviation kerosene/n-butanol blended fuel in a compression ignition engine

In order to meet the requirements of Sustainable Aviation Fuel (SAF) to achieve the imperatives of energy conservation and emission reduction. This paper compares the combustion characteristics of diesel, RP-3/n-butanol blends in terms of heat release rate, in-cylinder pressure, temperature and fuel economy in a compression ignition engine, taking into account the advantages of lightweight structure, low fuel consumption and wide range of applications of aviation piston engines. The results certified the viability of applying RP-3 and RP-3/n-butanol blends in diesel engines. Adding n-butanol prolonged the ignition delay and shorten the combustion duration. Moreover, the peak of the pressure, temperature and apparent heat release rate (AHRR) increased. In addition, the blended fuel showed obvious diffusion combustion characteristics at high load. With the n-butanol increased, the combustion instability of the blended fuels decreased significantly, at low load. At n = 2400r/min, pme = 0.53 MPa, compared with diesel, the maximum heat release rate (MHRR) of R70B30 increased by 76.6 %, improving the combustion characteristics of the blended fuel. Moreover, the equivalent specific fuel consumption (ESFC) of RP-3 is 5.56–14.83 % lower than that of diesel, and the effective thermal efficiency (ETE) of RP-3 is 2.8–13.46 % higher than that of diesel under most working conditions.

Analysis of geothermal heat recovery from abandoned coal mine water for clean heating and cooling: A case from Shandong, China

Exploiting heat from abandoned mine water using heat pumps is attracting increasing attention worldwide. China has a large number of abandoned coal mines, but there are few applications of geothermal heat recovery from mine water. Here, we report a new case from Shandong, North China. Based on actual geological and underground space structures, numerical analysis is performed to study the flow and heat transfer in the complex connection network among roadways. For given temperature differences on the source side, the underground heat transfer is greatly influenced by flow rates in roadways. Under the acceptable performances and long-term stability of heat pumps, the maximum heat transfer capacity of roadways reaches 697.3 kW at the flow rate of 100 m3/h, with the power per unit length of 151.3 W/m, indicating a promising heat recovery potential. When switching between the extraction and injection well, both fluid directions and the distribution of flow rates in roadways change obviously, thereby affecting the underground heat transfer. Besides dominant flow paths, there exist weak flow paths, which can be identified by numerical analysis, and necessary blocking can be applied to optimize the flow and heat transfer. Excessively long horizontal straight roadways for heat exchange should be avoided.

Quantifying flow regime impacts on hydrodynamic heat transfer in rough-walled rock fractures

Hydrodynamic heat transfer in rock fractures is crucial for many geophysical processes and engineering activities, notably in harnessing geothermal energy. Despite extensive research, characterizing hydrodynamic heat transfer in rock fractures, complicated by their geometric heterogeneity, remains a formidable challenge. To address this challenge, we experimentally investigated the hydrodynamic heat transfer in rock fractures with diverse geometric features at steady-state elevated temperatures. We found that both heterogeneous fracture geometry and elevated temperatures promote the transition of fracture flow from a linear to nonlinear regime. This flow regime transition enhances the heterogeneity of heat transfer intensity within the fracture and exacerbates the increase in heat transfer efficiency with flow rate. At a fortyfold increase in flow rate, the heat transfer coefficient in the most heterogeneous fracture rises by approximately 72 times, compared to about 28 times in the least heterogeneous one. Leveraging experimental data, we developed parametric models linking heat transfer coefficients, outflow temperature, and heat recovery rate to flow rate and geometric features, yielding a theoretical formulation for the maximal heat recovery rate. By introducing the concept of an energy conversion rate, we quantitatively evaluated the effect of nonlinear flow resistance on heat extraction feasibility, revealing that energy conversion rates in highly heterogeneous fractures can be up to 452 times lower than in less heterogeneous ones. This highlights the pivotal role of flow resistance in heat extraction feasibility. Our findings are instrumental for understanding and predicting the hydrodynamic heat transfer within fractured geothermal reservoirs and analogous hydro-thermal systems.

A Novel Plate Fin Heat Sink Design With Rectangular Slots and Interruptions: A Computational Approach

Abstract In the present work, we have studied the performance of vertical plate finned heat sinks that protrude from a vertical base. The difference between the heat sink base temperature and the ambient, i.e., ΔT, has been varied in the range of 10 °C to 60 °C, and the flow undergoes a natural convection regime. To enhance the thermal performance, we have explored different configurations of the heat sink by providing rectangular slots, varying the neck thickness, changing the neck location from the fin base, and providing interruptions along the fin height. The pertinent quantities, i.e., heat dissipation rate, Nusselt number, effectiveness, mass of heat sink, and heat dissipation per unit mass, have been obtained by performing 3D computational simulations. The results obtained are compared to assess the thermal performance of heat sinks. We found that among various designs of heat sinks proposed, the heat sink with two slots, with the location of neck closer to the fin base (xm = 9 mm), and with interrupted fins dissipates maximum heat (12.86% more compared to the commonly used rectangular plate finned heat sink). In addition to the heat transfer improvement, 19.82% mass reduction has also been achieved. Based on the simulation data, we have proposed a correlation for the mean Nusselt number as a function of relevant non-dimensional parameters.

Re-entry rocket basic flow characteristics and thermal environment of different retro-propulsion modes

During the supersonic re-entry of multi-nozzle heavy rockets into the atmosphere, the basic flow state becomes increasingly complex due to the coupling effect between the retro-propulsion plumes and the freestream. A numerical method using the hybrid Reynolds-Averaged Navier-Stokes and Large Eddy Simulation (RES) method and discrete coordinate method is developed to accurately estimate the thermal environment. In addition, finite rate chemical kinetics is used to calculate the afterburning reactions. The numerical results agree well with wind tunnel data, which confirms the validity and accuracy of the numerical method. Computations are conducted for the heavy carrier rocket re-entry from 53.1 km to 39.5 km altitude with 180° angle of attack by using three different Supersonic Retro-Propulsion (SRP) modes. The numerical results reveal that these three SRP flow fields are all Short Penetration Models (SPM). As the re-entry altitudes decrease, both the plume-plume interaction and the plume-freestream interaction become weaker. The highest temperatures in the plume shear layers of the three SRP modes increase by 8.36%, 7.33% and 6.92% respectively after considering afterburning reactions, and all occur at a re-entry altitude of 39.5 km. As the rocket re-enters the atmosphere, the maximum heat flux on the rocket base plate of three SRP modes stabilizes at 290, 170 and 200 kW/m2 respectively, but the maximum heat flux on the side wall increases significantly. When the altitude declines to 39.5 km, the extreme heat flux of the three modes increase by 84.16%, 49.45% and 62.97% respectively compared to that at 53.1 km.

Hazard comparison of thermal runaway of electric marine battery cabinet under different trigger modes

Currently, the transportation industry, especially shipping, is still accompanied by serious carbon emissions and pollution. Electric ships are the most promising way to solve this problem. However, the application of electric ships in maritime affairs also faces many technical difficulties. This paper studies the heat generation and heat transfer in electric Marine battery cabinets (EMBC). Based on the Multi-Scale and Multi-Domain (MSMD) solution method, this study uses the Newman, Tiedemann, Gu, and Kim (NTGK) battery model to solve the thermal runaway propagation (TRP) of the EMBC, and then makes a visual analysis of the TRP of the EMBC with the three-layer Battery module (BM) structure. Furthermore, the TRP of the three-layer BM is compared based on three different triggering modes. Through analysis and comparison, it is found that among the three TR triggering modes: single battery heating, heat source at the bottom of the module, and heat source at the top. The first mode corresponds to a maximum heat release (HR) of 214.7 GJ, while the third mode exhibits a minimum HR of 212.3 GJ. Furthermore, the maximum temperature reached by the battery under the third mode is 1568 K, which is lower than that achieved in the other two modes. Additionally, it should be noted that the second mode has a higher maximum HR rate of 5772 GW/m3 compared to the third mode. The TR hazard resulting from heating at the bottom of the battery module outweighs that caused by heating at the top, without taking into account human-induced heating factors. The propagation of TR triggered by a single heat source throughout the EMBC can be inhibited within 226 s in the same layer, and prevented from spreading to the remaining layers for up to 596 s. In the present study, a new insight is presented to reveal the TR characteristics of the EMBC under different triggering modes, and quantify the TR duration.

Amplification of the discrepancy between simplified and physics-based wet-bulb globe temperatures in a warmer climate

The Simplified Wet Bulb Globe Temperature (sWBGT) is widely used in heat stress assessments for climate-change studies, but its limitations have not been thoroughly explored. Building on recent critiques of sWBGT's use for current climate on global scale, this study examines sWBGT's biases using dynamically-downscaled sub-daily climate projections under multiple future emission scenarios. The analysis is aimed at understanding caveats in the application of sWBGT and the uncertainties in existing climate change analysis dependent on sWBGT. Results indicate sWBGT's biases are heavily influenced by local near-surface air temperature, with overestimation of heat stress in East Asia regions, particularly hot and humid areas, due to static assumptions of radiation and wind speed. This overestimation is amplified in warmer climates, leading to exaggerated projected heat stress increases in future. In contrast, underestimations are found for heat stress levels attributed to low wind speeds and strong radiations, such as over the Tibetan Plateau and certain extreme events. Additionally, sWBGT underestimates variability in extreme heatwave events compared to WBGT in both current and future climates, irrespective of overestimation in absolute heatwave intensities. This study emphasizes the limitations of sWBGT, especially in future warmer climates. Importance of sub-daily data for capturing daily maximum heat stress level and reflecting diurnal variations in different components is also discussed. In conclusion, we recommend using Liljegren's model (i.e., physics-based calculation) with high-resolution sub-daily climate data for more accurate outdoor heat stress assessments in climate change studies.

Clean energy pipeline energy storage system and its economy

The economic problem of a clean energy heating system under a peak and valley electricity pricing system is investigated, and a pipe network energy storage system is correspondingly proposed to solve this problem. The system makes use of large-capacity primary network pipe network water storage to store heat during the valley electricity hours when the electricity price is lower, and releases the stored heat to supply heat during the peak electricity hours when the electricity price is higher, with a view to reducing the operating time of the heating system during the peak electricity hours when the electricity price is higher. The principle of the system and the efficient regulation scheme are given, and a mathematical model of primary pipe network energy storage and release is established, and the reliability of the model is verified with a heating project in Qingdao as an example, and the results show that the maximum temperature deviation of the return temperature of the primary pipe network obtained by the calculation of the energy storage and release model is 0.23 °C, and the maximum temperature hysteresis error is in 15 %, which meets the requirements of engineering practice. Based on the energy storage model, the simulation of the actual heating economy of the project using the pipe network energy storage system was carried out, and the results showed that compared with the original scheme based on the maximum heat load adjustment of the proportion of heating units and boilers, the electricity consumption of the project using the pipe network heat storage scheme was increased by 18.8 % in the whole heating season, the total operating costs were reduced by 14.5 %, with an annual saving of 800,600 yuan in operating costs, and the payback period for the investment was relatively short, at 2.1 years, which is of good economy.

Infrared thermography detection of grouting defects in post-tensioned tendon ducts under active thermal excitation

The efficacy of employing infrared thermography (IRT) for concrete bridge deck inspection has been well established. Although an IRT detection method during construction stage under hydration heat excitation had been proposed in old works, it is also essential to be applicated in the existing large amounts of bridges in service, while it can be challenging due to factors, such as the substantial depth of the ducts and the variation in duct materials. Therefore, this study presents an IRT detection method for grouting defects in post-tensioned tendon ducts under the stimulation of a shortwave infrared heater. The investigation explores the influence of different factors, such as duct depth, length, grouting compactness level, and duct material, on the detection results and the corresponding heating durations required. Results indicate that with a thermal radiation intensity of approximately 550 W/m2 with a heating duration of 45 mins and followed by a cooling period of 90 mins to 130 mins, the detection of fully grouted void defects within 350 mm long ducts made of polyvinyl chloride (PVC) at burial depths of 50, 70, and 90 mm is feasible. For the best detection results, grouting void defects buried at a depth of 50 mm should be detected after a maximum heating duration of 75 mins and 90 mins corresponding to the PVC ducts and metal ducts. The detection effectiveness is higher for PVC ducts than for metal ducts. Furthermore, an environmental impact analysis should be carried out in the future to make this method into practice.

Liquid–liquid transition and ice crystallization in a machine-learned coarse-grained water model

Mounting experimental evidence supports the existence of a liquid-liquid transition (LLT) in high-pressure supercooled water. However, fast crystallization of supercooled water has impeded identification of the LLT line TLL(p) in experiments. While the most accurate all-atom (AA) water models display a LLT, their computational cost limits investigations of its interplay with ice formation. Coarse-grained (CG) models provide over 100-fold computational efficiency gain over AA models, enabling the study of water crystallization, but have not yet shown to have a LLT. Here, we demonstrate that the CG machine-learned water model Machine-Learned Bond-Order Potential (ML-BOP) has a LLT that ends in a critical point at pc = 170 ± 10 MPa and Tc = 181 ± 3 K. The TLL(p) of ML-BOP is almost identical to the one of TIP4P/2005, adding to the similarity in the equation of state of liquid water in both models. Cooling simulations reveal that ice crystallization is fastest at the LLT and its supercritical continuation of maximum heat capacity, supporting a mechanistic relationship between the structural transformation of water to a low-density liquid (LDL) and ice formation. We find no signature of liquid-liquid criticality in the ice crystallization temperatures. ML-BOP replicates the competition between formation of LDL and ice observed in ultrafast experiments of decompression of the high-density liquid (HDL) into the region of stability of LDL. The simulations reveal that crystallization occurs prior to the coarsening of the HDL and LDL domains, obscuring the distinction between the highly metastable first-order LLT and pronounced structural fluctuations along its supercritical continuation.

STUDY OF THE INFLUENCE OF MODIFIERS ON THE HYDRATION OF CEMENT BY THE METHOD OF ISOTHERMAL CALORIMETRY

The effect of modifiers on the hydration of cements was studied by isothermal calorimetry. Thermochemical experiments were carried out using a TAM III isothermal calorimeter (TA Instruments). For the TAM III calorimeter, a method was developed for conducting experiments on monitoring the thermal activity of solid-phase samples with the possibility of repeated use of steel ampoules with a volume of 20 ml. The processes of hydration of Portland cement grade CEM I 42.5B D0 LLC "Holcim Rus" without a modifier and with modifiers polycarboxylate type S (POLYPLAST LLC and «Glass Powder) were studied. Heat release thermograms were recorded, which showed good reproducibility of the results and their similarity with those available in the literature for similar studies carried out according to standard methods using a TAM AIR isothermal calorimeter (TA Instruments). This indicates the reliability of the obtained data and the possibility of using the method proposed in this article to study the processes of hydration of cements. The maximum heat release on the thermograms of samples with a polycarboxylate modifier is observed approximately 20 h after the start of heat release monitoring. Samples without the modifier and with the glass powder modifier show the maximum heat release approximately 10 h after the start of the experiment. Analysis of the results showed that the presence of modifiers leads to increased heat release during cement hydration in relation to its initial composition. Accordingly, it takes less time to complete hydration. However, it is also necessary to take into account the possible risks of violation of the technological modes of operation of the corresponding equipment due to excessive heat release during the hydration of modified cements. For citation: Usacheva T.R., Krainova A.A., Vinogradova L.A., Oganyan V.V., Kokurina G.N., Myshenkov M.S., Anufrikov Yu.A., Shasherina A.Yu., Adamtsevich A.O. Study of the influence of modifiers on the hydration of cement by the method of isothermal calorimetry. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 6. P. 88-93. DOI: 10.6060/ivkkt.20246706.6979.

Heat Transfer Process of the Tea Plant under the Action of Air Disturbance Frost Protection

Wind machines based on the air disturbance method are progressively employed to mitigate frost damage within the agricultural machinery frost protection. These devices are utilized during radiative frost nights to disrupt near-surface thermal inversion through air mixing. Despite this application, the fundamental mechanisms underlying these mixing processes are not well comprehended. In this research, numerical simulations were conducted using COMSOL Multiphysics software version 6.0 to simulate the flow and heat transfer processes between the thermal airflow and both the tea canopy and stems. The results indicated that due to obstruction from the canopy cross-section, the airflow velocity on the contact surface rapidly increased. As the airflow further progressed, the high-speed region of the airflow gradually approached the canopy surface. Turbulent kinetic energy increased initially on the windward side of the canopy cross-section and near the top interface. On the windward side of the canopy, due to the initial impact of the thermal airflow, rapid heating occurred, resulting in a noticeable temperature difference between the windward and leeward sides within a short period. In the interaction between airflow and stems, with increasing airflow velocity, fluctuations and the shedding of wake occurred on the leeward side of the stems. The maximum sensible heat flux at the windward vertex of the stem increased significantly with airflow velocity. At an airflow velocity of 2.0 m/s, the maximum heat flux value was 2.37 times that of an airflow velocity of 1.0 m/s. This research utilized simulation methods to study the interaction between airflow and tea canopy and stems in frost protection, laying the foundation for further research on the energy distribution in tea ecosystem under the disturbance of airflow for frost protection.

Performance improvement of the phase change material-assisted earth-air heat exchanger in summer

Studies confirmed that phase change material (PCM) can improve the cooling potential of an earth-air heat exchanger (EAHE). However, the poor utilization of the PCM unit’s latent heat storage (LHS) capacity and insufficient understanding of energy efficiency hinder its applications in EAHE. To solve these problems, this study made a structural improvement to the PCM unit and proposed a centrally located hollow cylindrical PCM-assisted EAHE (CHCPCM-EAHE). Then, numerical simulations were conducted on this CHCPCM-EAHE through a 3-D model built on the ANSYS FLUENT, and its cooling performance in Chongqing (China) summer was comparatively studied. The results found that the LHS performance of the PCM unit in this CHCPCM-EAHE was improved despite the significant reduction in material volume. Compared to the PCM unit in the previous PCM-assisted EAHE, the maximum liquid fraction and average charged latent heat in all charge–discharge cycles of the PCM unit in this CHCPCM-EAHE were increased by 56.82 % and 10.46 %∼56.43 %, respectively. The results also found that the CHCPCM-EAHE performed better in cooling potential and coefficient of performance (COP). Compared to the conventional EAHE and previous PCM-assisted EAHE, its average cooling capacity increased by 60.12 %∼70.75 % and 4.05 %∼10.96 %, and average COP increased by 47.22 %∼49.02 % and 6.88 %∼8.18 %, respectively.

Effect of Sowing Direction and Wheat Cultivars on Growth and Yield in Indo-Gangetic Plains of India

A field experiment was carried out during rabi season where different wheat cultivars (PBW-343, HUW-234 and NW-1012) and direction of sowing (E-W and N-S) were taken in Factorial Randomized Block Design replicated four times. All the yield attributing characters like number of effective tillers, spike length, number of grains spike–1, grain weight spike–1 were significantly higher under East-West direction of sowing over North-South direction of sowing. Among the all cultivars PBW-343 was found significantly superior over NW-1012 and HUW-234. The grain yield, straw yield and light intensity were increased significantly under East-West direction of sowing and among the cultivars PBW-343 recorded significantly higher value of above characters over NW-1012 and HUW-234. Maximum heat unit requirement and days taken to 50% ear emergence and maturity was recorded under North-South direction of sowing and among the cultivars it was found maximum in PBW-343. The maximum net return and B:C ratio were obtained in E-W direction of sowing along with PBW-343 cultivar. Thus it may be revealed that sowing in East-West direction with cultivar PBW-343 was found most suitable for cultivation under Indo-Gangetic Plains of India.

Omnidirectional simulation analysis of thermo-mechanical coupling mechanism in inertia friction welding of Ni-based superalloy

The coupling between heat and pressure is the kernel of inertia friction welding (IFW) and is still not fully understood. A novel 3D fully coupled finite element model based on a plastic friction pair was developed to simulate the IFW process of a Ni-based superalloy and reveal the omnidirectional thermo-mechanical coupling mechanism of the friction interface. The numerical model successfully simulated the deceleration, deformation processes, and peak torsional moments in IFW and captured the evolution of temperature, contact pressure, and stress. The simulated results were validated through measured thermal history, optical macrography, and axial shortening. The results indicated that interfacial friction heat was the primary heat source, and plastic deformation energy only accounted for 4% of the total. The increase in initial rotational speed and friction pressure elevated the peak temperature, reaching a maximum of 1525.5 K at an initial rotational speed of 2000 r/min and friction pressure of 400 MPa. The interface heat generation could form an axial temperature gradient exceeding 320 K/mm. The radial inhomogeneities of heat generation and temperature were manifested in a concentric ring distribution with maximum heat flux and temperature ranging from 2/5 to 2/3 radius. The radial inhomogeneities were caused by increasing linear velocity along the radius and an opposite distribution of contact pressure, which could reach 1.7 times the set pressure at the center. The circumferential inhomogeneity of thermo-mechanical distribution during rotary friction welding was revealed for the first time, benefiting from the 3D model. The deflection and transformation of distribution in contact pressure and Mises stress were indicators of plastic deformation and transition of quasi-steady state welding. The critical Mises stress was 0.5 times the friction pressure in this study. The presented modeling provides a reliable insight into the thermo-mechanical coupling mechanism of IFW and lays a solid foundation for predicting the microstructures and mechanical properties of inertia friction welded joints.

Numerical study on thermal runaway in a cell and battery pack at critical heating conditions with variation in heating powers

The thermal stability of lithium-ion cell is still a major concern in electric vehicle and energy storage applications affecting the cell to its chemistry level. The thermal abuse is the most common type of thermal runaway which is triggered either by excess heat accumulation or localized heating in the battery pack. Analysis of thermal runaway in the perspective of various critical heating positions with temperature distribution, heat generation still lacks. Thus, the present work is focused on this issue. A three-dimensional homogeneous Multi-Scale, Multi-Dimensional model with a finite volume method solver ANSYS FLUENT has been utilised to assess the effect of heating positions, and variation in spacings on thermal runaway for a 18650 cell and battery pack in a detailed way. It is observed that the direction of flow is the typical deciding factor of the thermal runaway spreading pattern in the cell. The negative solvent is responsible for the generation of maximum heat in the thermal runaway of a 18650 cell. The results show that cell heated at the bottom end (10 mm width) is fast prone to thermal runaway, vertical (5 mm width) being slower in disturbing the separator stability. The NCA cathode material has a safety hierarchy that goes as follows with regard to positions: vertical 10 mm > bottom end > bottom 5 mm > centre 10 mm > bottom 10 mm. The effect of spacing on thermal runaway is varying non-uniformly with the location of the heating position in the 3 × 3 battery pack. The highest temperature attained by the 7000 W/m2 heating power battery pack is discovered to be greater than the 10,000 W/m2 by 10 K. With a power increase from 7000 W/m2 to 10,000 W/m2, there is a reduction in time delay of 17 %.

Comparative Analysis of Influencing Factors on Heat Extraction Performance of Multi-Type Shallow Borehole Heat Exchangers

In this paper, the influence of design parameters and geological parameters on the heat extraction capacity of common coaxial type, single U-type, and double U-type borehole heat exchangers(BHEs) in shallow ground source heat pump system is analyzed, and the heat extraction performance of different types of BHEs is further compared. The results show that with the increase in borehole depth and ground temperature gradient, the outlet temperature of the three types increases at the end of the heating season, and the single U-type BHE increases most significantly. The increase in inlet flow rate will decrease the outlet temperature of the three BHEs, and the U-type is the most obvious decrease. The increase in inlet temperature will reduce the temperature difference between inlet and outlet of the three types BHEs. Given the same design parameters, coaxial-type BHE obtains the maximum heat.

A tentative study on the effect of tunnel width on the maximum temperature under the ceiling in tunnel fires

Maximum gas temperature under the ceiling in tunnel fires has been studied experimentally and numerically. Full scale burning test in tunnel with length 100 is carried out. Three different pool fires with approximate maximum heat release rate of 0.6, 1.0 and 5MW were set up. The smoke temperature is collected by the Fiber-optic Bragg grating system. CFD simulations were carried out to study the effect of tunnel width on the maximum temperature. By analyzing the experimental and numerical simulation results, a critical point of ratio B/H and two stages concerning the varying of B/H are proposed to clarify the influence of tunnel width, meanwhile we conclude that it is interdependent between the ratio of H/B and the ventilation velocity when discussing the maximum gas temperature in tunnel fires.