Personal Thermal Management by Radiative Cooling and Heating

Maintaining thermal comfort within the human body is crucial for optimal health and overall well-being.By merely broadening the setpoint of indoor temperatures,we could significantly slash energy usage in building heating,ventilation,and air-conditioning systems.In recent years,there has been a surge in advancements in personal thermal management(PTM),aiming to regulate heat and moisture transfer within our immediate surroundings,clothing,and skin.The advent of PTM is driven by the rapid development in nano/micro-materials and energy science and engineering.An emerging research area in PTM is personal radiative thermal management(PRTM),which demonstrates immense potential with its high radiative heat transfer efficiency and ease of regulation.However,it is less taken into account in traditional textiles,and there currently lies a gap in our knowledge and understanding of PRTM.In this review,we aim to present a thorough analysis of advanced textile materials and technologies for PRTM.Specifically,we will introduce and discuss the underlying radiation heat transfer mechanisms,fabrication methods of textiles,and various indoor/outdoor applications in light of their different regulation functionalities,including radiative cooling,radiative heating,and dual-mode thermoregulation.Furthermore,we will shine a light on the current hurdles,propose potential strategies,and delve into future technology trends for PRTM with an emphasis on functionalities and applications.

Thermal comfort assessment and energy consumption analysis of ground-source heat pump system combined with radiant heating/cooling

A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building： Xijindu exhibition hall, which is located in Zhenjiang city in China. Numerical studies on the thermal comfort and energy consumption of the system are carded out by using TRNSYS software. The results indicate that the system with the radiant floor method or the radiant ceiling method shows good thermal comfort without mechanical ventilation in winter. However, the system with either of the methods should add mechanical ventilation to ensure good comfort in summer. At the same level of thermal comfort, it can also be found that the annual energy consumption of the radiant ceiling system is less than that of the radiant floor system.

Thin paints for durable and scalable radiative cooling

Passive daytime radiative cooling(PDRC) is environment-friendly without energy input by enhancing the coating's solar reflectance(R_(solar)) and thermal emittance(ε_(LWIR)) in the atmosphere's long-wave infrared transmission window.However,high R_(solar) is usually achieved by increasing the coating's thickness,which not only increases materials' cost but also impairs heat transfer.Additionally,the desired high R_(solar) is vulnerable to dust pollution in the outdoors.In this work,a thin paint was designed by mixing hBN plates,PFOTS,and IPA. R_(solar)=0.963 and ε_(LWIR)=0.927 was achieved at a thickness of 150 μm due to the high backscattering ability of scatters.A high through-plane thermal conductivity(~1.82 W m^(-1) K^(-1)) also can be obtained.In addition,the porous structure coupled with the binder PFOTS resulted in a contact angle of 154°,demonstrating excellent durability under dust contamination.Outdoor experiments showed that the thin paint can obtain a 2.3℃ lower temperature for sub-ambient cooling than the reference PDRC coating in the daytime.Furtherly,the above-ambient heat dissipation performance can be enhanced by spraying the thin paint on a 3D heat sink,which was 15.7℃ lower than the reference 1D structure,demonstrating excellent performance for durable and scalable PDRC applications.

Adaptive battery thermal management systems in unsteady thermal application contexts

With the increasing attention paid to battery technology,the microscopic reaction mechanism and macroscopic heat transfer process of lithium-ion batteries have been further studied and understood from both academic and industrial perspectives.Temperature,as one of the key parameters in the physical fra mework of batteries,affects the performa nce of the multi-physical fields within the battery,a nd its effective control is crucial.Since the heat generation in the battery is determined by the real-time operating conditions,the battery temperature is essentially controlled by the real-time heat dissipation conditions provided by the battery thermal management system.Conventional battery thermal management systems have basic temperature control capabilities for most conventional application scenarios.However,with the current development of la rge-scale,integrated,and intelligent battery technology,the adva ncement of battery thermal management technology will pay more attention to the effective control of battery temperature under sophisticated situations,such as high power and widely varied operating conditions.In this context,this paper presents the latest advances and representative research related to battery thermal management system.Firstly,starting from battery thermal profile,the mechanism of battery heat generation is discussed in detail.Secondly,the static characteristics of the traditional battery thermal management system are summarized.Then,considering the dynamic requirements of battery heat dissipation under complex operating conditions,the concept of adaptive battery thermal management system is proposed based on specific research cases.Finally,the main challenges for battery thermal management system in practice are identified,and potential future developments to overcome these challenges are presented and discussed.

Optimized scheduling of integrated energy systems for low carbon economy considering carbon transaction costs

With the introduction of the“dual carbon”goal and the continuous promotion of low-carbon development,the integrated energy system(IES)has gradually become an effective way to save energy and reduce emissions.This study proposes a low-carbon economic optimization scheduling model for an IES that considers carbon trading costs.With the goal of minimizing the total operating cost of the IES and considering the transferable and curtailable characteristics of the electric and thermal flexible loads,an optimal scheduling model of the IES that considers the cost of carbon trading and flexible loads on the user side was established.The role of flexible loads in improving the economy of an energy system was investigated using examples,and the rationality and effectiveness of the study were verified through a comparative analysis of different scenarios.The results showed that the total cost of the system in different scenarios was reduced by 18.04%,9.1%,3.35%,and 7.03%,respectively,whereas the total carbon emissions of the system were reduced by 65.28%,20.63%,3.85%,and 18.03%,respectively,when the carbon trading cost and demand-side flexible electric and thermal load responses were considered simultaneously.Flexible electrical and thermal loads did not have the same impact on the system performance.In the analyzed case,the total cost and carbon emissions of the system when only the flexible electrical load response was considered were lower than those when only the flexible thermal load response was taken into account.Photovoltaics have an excess of carbon trading credits and can profit from selling them,whereas other devices have an excess of carbon trading and need to buy carbon credits.

Analysis of influence of heat exchangerfouling on heat transfer performancebased on thermal fluid coupling

A study on heat transfer performance by thermal fluid coupling simulation for the fouling in a shell-tube heat exchanger used in engineering was presented. The coupling simulation was performed in a fluid and solid domains under three different fouling conditions: fouling inside the tube, fouling outside the tube, and fouling inside the shell. The flow field, temperature, and pressure distributions in the heat exchanger were solved numerically to analyze the heat transfer performance parameters, such as thermal resistance. It is found that the pressure drop of the heat exchanger and the thermal resistance of the tube wall increase by nearly 30% and 20%, respectively, when the relative fouling thickness reaches 10%. The fouling inside the tube has more impact on the heat transfer performance of the heat exchanger, and the fouling inside the shell has less impact.

Tectonic-thermal history and hydrocarbon potential of the Pearl River Mouth Basin,northern South China Sea:Insights from borehole apatite fission-track thermochronology

The Pearl River Mouth Basin(PRMB)is one of the most petroliferous basins on the northern margin of the South China Sea.Knowledge of the thermal history of the PRMB is significant for understanding its tectonic evolution and for unraveling its poorly studied source-rock maturation history.Our investigations in this study are based on apatite fission-track(AFT)thermochronology analysis of 12 cutting samples from 4 boreholes.Both AFT ages and length data suggested that the PRMB has experienced quite complicated thermal evolution.Thermal history modeling results unraveled four successive events of heating separated by three stages of cooling since the early Middle Eocene.The cooling events occurred approximately in the Late Eocene,early Oligocene,and the Late Miocene,possibly attributed to the Zhuqiong II Event,Nanhai Event,and Dongsha Event,respectively.The erosion amount during the first cooling stage is roughly estimated to be about 455-712 m,with an erosion rate of 0.08-0.12 mm/a.The second erosion-driven cooling is stronger than the first one,with an erosion amount of about 747-814 m and an erosion rate between about 0.13-0.21 mm/a.The erosion amount calculated related to the third cooling event varies from 800 m to 3419 m,which is speculative due to the possible influence of the magmatic activity.

Heat transfer and parametric studies of an encapsulated phase change material based cool thermal energy storage system

This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES) system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature histories of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. The model was also used to investigate the effect of porosity, Stanton number, Stefan number and Peclet number on CTES system performance. The results showed that increase in porosity contributes to a higher rate of energy storage. However, for a given geometry and heat transfer coefficient, the mass of PCM charged in the unit decreases as the increase in porosity. The St number as well as the Ste number is also influential in the performance of the unit. The model is a convenient and more suitable method to determine the heat transfer characteristics of CTES system. The results reported are much useful for designing CTES system.

Heat absorption control equation and its application of cool-wall cooling system in mines

In order to solve the heat damages in deep mines, a cool-wall cooling technology and its working model are proposed based on the principles of heat absorption and insulation in this paper. During this process, the differential equation of thermal equilibrium for roadway control unit is built, and the heat adsorption control equation of cool-wall cooling system is derived by an integral method, so as to obtain the quantitative relationship among the heat absorption capacity of cooling system, the heat dissipating capacity of surrounding rock and air temperature change. Then, the heat absorption capacity required by air temperature less than the standard value for safety is figured out by section iterative method with the simultaneous solution of heat absorption control equation and the heat dissipation density equation of surrounding rock. Finally, the results show that as the air temperature at the inlet of roadway is 25 ℃, the roadway wall is covered by heat-absorbing plate up to 39% of the area, as well as the cold water is injected into the heat-absorbing plate with a temperature of 20 ℃ and a mass flow of 113.6 kg/s, the air flow temperature rise per kilometer in the roadway can be less than 3 ℃.

Energy Efficient Air Conditioning System Using Geothermal Cooling-Solar Heating in Gujarat, India

It is well known that one unit of electrical energy saved is equal to more than two units produced. One way of economizing the power is utilization of energy efficient systems at all locations. In the present study, the air conditioning system is analysed and an innovative way is suggested. We use natural low temperature of shallow sub surface (1 - 3 m) of the earth—geothermal cooling system. It is known that majority of the households and the apartment complexes in India have two tanks for water storage. One is the underground water sump and the other is the overhead water tank. In our study, we use these two water storage systems for space cooling during summer and also for heating during winter. The main aim of our paper is air-conditioning of the space in an economic way to save electricity. It is based on a simple idea of transferring the low temperature from underground water sump to the room in the house using water as a mode of transport. Since India is a tropical country located at low latitude, most of the year, the air temperature is high and demands space cooling. However, for a couple of months during severe winter months (Dec.-Jan.) at Ahmedabad, heating of the space is required. For heating the space, we suggest to use the well-known solar water heater. Effective use of heat exchanger is shown through computation, modelling schemes and lab experiment. We recommend geothermal cooling for 10 months in a year and solar hot water system during 2 months of winter. It is observed that the ambient air temperature of 35°C - 40°C in the room can be brought down to 26°C without much consumption of electricity. In a similar manner, the room temperature at night (13°C) during winter in Ahmedabad can be increased to 27°C through circulation of water from solar water heater in the heat exchanger.

Fast Calculation Method of Energy Flow for Combined Electro-Thermal System and Its Application

In recent years, Combined electro-thermal system has developed rapidly. In order to provide the initial data for the analysis of the combined electro-thermal system, a practical energy flow calculation method for the combined electro-thermal system is proposed in this paper. Based on the detailed analysis of the topology structure of the heating network and its hydraulic and thermodynamic model, the forward-backward sweep method for the heat flow of the heating network is established, which is more suitable for the actual radial heating network. The electric and thermal coupling model for heating source, such as thermoelectric unit and electric boiler is established, and the heat flow of heating network and the power flow of power grid are calculated orderly, thus a fast calculation method for the combined electro-thermal system is formed. What’s more, a combined electro-thermal system with two-stage peak-shaving electric boiler is used as the example system. This paper validates the effectiveness and rapidity of this method through the example system, and analyzes the influence for the energy flow of combined electro-thermal system caused by the operating parameters such as the installation location of electric boiler, the outlet water temperature of heat source and the outlet flow rate, etc.

Investigation of Thermal Losses in a Soft Magnetic Composite Using Multiphysics Modelling and Coupled Material Properties in an Induction Heating Cell

The complex interaction between material properties in an induction heating circuit was studied by multi physics simulation and by experimental verification in a full-scale laboratory heater. The work aims to illustrate the complexity of the system of interacting materials, but also to propose a method to verify properties of soft magnetic composite materials in an integrated system and to identify which properties are the most critical under different circumstances and load cases. Heat losses at different loads were primarily studied, from DC currents to AC currents at 15, 20 and 25 kHz, respectively. A FE model for magnetic simulation was correlated with a corresponding model for heat simulation. The numerical model, as well as the established input material data, could be verified through the experimental measurements. In this particular study, the current loss in the litz wire was the dominant heat source, thus making the thermal conductivity of the SMC the most important property in this material.

Interpretation of gas-film cooling against aero-thermal heating for high-speed vehicles

The possible application of the film-cooling technique against aero-thermal heating for surfaces of high-speed flying vehicles is discussed. The technique has been widely used in the heat protection of gas turbine blades. It is shown in this paper that, by applying this technique to high-speed flying vehicles, the working principle is fundamentally different. Numerical simulations for two model problems axe performed to support the argument. Besides the heat protection, the appreciable drag reduction is found to be another favorable effect. For the second model problem, i.e., the gas cooling for an optical window on a sphere cone, the hydrodynamic instability of the film is studied by the linear stability analysis to observe possible occurrence of laminar-turbulent transition.

HEAT TRANSFER CHARACTERISTICS OF NEW COOLING TECHNIQUE BASED ON THERMAL DRIVING

A new cooling technique based on thermal driving in high centrifugal field （TDHCF） is developed for gas turbine rotational components, such as turbine blades. The key point of TDHCF is to enhance heat transfer by the fluid thermal driving in closed loop small channels placed in the high centrifugal field. Heat transfer characteristics of the new cooling technique are analyzed. In experiments, two different fluids （liquid water and Freon R12） are used as thermal driving media （fluid inside the loop channel）. And the channel width d is 1 mm and the height h is 30 mm. The temperature is measured by thermocouples and an average heat transfer coefficient KH is defined to indicate heat transfer capacity of TDHCF. Experimental results show that KH is enhanced when heat flux and the rotating speed increase. And thermal properties of thermal driving media are also influenced by KH. Larger KH can be achieved by using Freon R12 as thermal driving medium compared with using liquid water. It can increase to 2 300 W/（m^2 · K） and it is much higher than that of the normal air cooling method （usually at the level of 600-1200 W/（m^2·K））. All fundamental studies of TDHCF show that there actually exists thermal driving in the closed loop small channel in the centrifugal field to improve heat transfer characteristics.

Thermal Management of Vehicle Cabins,External Surfaces,and Onboard Electronics:An Overview

Reducing heat accumulation within vehicles and ensuring appropriate vehicular temperature levels can lead to enhanced vehicle fuel economy,range,reliability,longevity,passenger comfort,and safety.Advancements in vehicle thermal management remain key as new technologies,consumer demand,societal concerns,and government regulations emerge and evolve.This study summarizes several recent advances in vehicle thermal management technology and modeling,with a focus on three key areas:the cabin,electronics,and exterior components of vehicles.Cabin-related topics covered include methods for reducing thermal loads and improving heating,ventilation,and air-conditioning(HVAC)systems;and advancements in window glazing/tinting and vehicle surface treatments.For the thermal management of electronics,including batteries and insulated-gate bipolar transistors(IGBTs),active and passive cooling methods that employ heat pipes,heat sinks,jet impingement,forced convection,and phase-change materials are discussed.Finally,efforts to model and enhance the heat transfer of exterior vehicular components are reviewed while considering drag/friction forces and environmental effects.Despite advances in the field of vehicle thermal management,challenges still exist;this article provides a broad summary of the major issues,with recommendations for further study.

Fabrication and thermal performance of grooved-sintered wick heat pipe

Some novel grooved-sintered composite wick heat pipes(GSHP) were developed for the electronic device cooling.The grooved-sintered wicks of GSHP were fabricated by the processes of oil-filled high-speed spin forming and solid state sintering.The wick could be divided into two parts for liquid capillary pumping flow:groove sintered zone and uniform sintered zone.Both of the thermal resistance network model and the maximum heat transfer capability model of GSHP were built.Compared with the theoretical values,the heat transfer limit and thermal resistance of GSHP were measured from three aspects:copper powder size,wick thickness and number of micro grooves.The results show that the wick thickness has the greatest effect on the thermal resistance of GSHP while the copper powder size has the most important influence on the heat transfer limit.Given certain copper powder size and wick thickness,the thermal resistance of GSHP can be the lowest when micro-groove number is about 55.

Experimental Study on the Thermal Performances of a Tube-Type Indirect Evaporative Cooler

The so-called indirect evaporative cooling technology is widely used in air conditioning applications.The thermal characterization of tube-type indirect evaporative coolers,however,still presents challenges which need to be addressed to make this technology more reliable and easy to implement.This experimental study deals with the performances of a tube-type indirect evaporative cooler based on an aluminum tube with a 10 mm diameter.In particular,the required tests were carried out considering a range of dry-bulb temperatures between 16℃ and 18℃ and a temperature difference between the wet-bulb and dry-bulb temperature of 2℃∼4℃.The integrated convective heat transfer coefficient inside the tube in the drenching condition has been found to lie in the range between 36.10 and 437.4(W/(m^(2)⋅K)).

A Thermal Analogue of the Zel’Dovich Effect

We analyze in this work anisotropic heat conduction induced by a harmonically oscillating laser source incident on rotating conductors, exploiting an analogy with an effect discovered long ago, called the Zel’dovich effect. We re-covered the main results of a recently published paper that predicts the translational Doppler frequency shift of a thermal wave induced on a sample moving with uniform rectilinear motion. We extend then this framework to take into account the frequency shift of a thermal field propagating on a rotating platform. We show that it coincides with the rotational frequency shift which has been recently observed on surface acoustic waves and hydrodynamic surface waves, called rotational superradiance. Finally, we use an analogy with the Tolman effect to deduce a simple estimate of the average temperature gradient induced by rotation, showing the existence of a new cooling effect associated with heat torque transfer.

STAR CCM+ CFD Simulations of Enhanced Heat Transfer in High-Power Density Electronics Using Forced Air Heat Exchanger and Pumped Fluid Loop Cold Plate Fabricated from High Thermal Conductivity Materials

As telecommunication and RF power electronics applications continue to push the envelope of waste heat dissipation, more and more, we see a need for active thermal control employing forced air electronic cooling fans in unison with pumped fluid loops in order to meet temperature and performance requirements. This research paper presents results of applying Computational Fluid Dynamics (CFD) commercial industry STAR-CCM+ software for heat transfer and fluid flow simulation of a novel heat exchanger/cold plate fabricated from k-core high thermal conductivity material in order to realize thermal control system hardware design for very much applications to very large power density (~1 kW/m2) electronics packaging scenarios. Trade studies involving different heat exchanger/cold plate materials, as well as vari- ous fault scenarios within a mock-up of a typical electronics system, are used to illustrate the upper bounds placed on the convective heat transfer coefficient. Agreement between our present findings and previous research in the field of electronics cooling is presented herein.

Thermal modeling optimization and experimental validation for a single concentrator solar cell system with a heat sink

A single concentrator solar cell model with a heat sink is established to simulate the thermal performance of the system by varying the number, height, and thickness of fins, the base thickness and thermal resistance of the thermal conductive adhesive. Influence disciplines of those parameters on temperatures of the solar cell and heat sink are obtained. With optimized number, height and thickness of fins, and the thickness values of base of 8, 1.4 cm, 1.5 mm, and 2 mm, the lowest temperatures of the solar cell and heat sink are 41.7 ~C and 36.3 ~C respectively. A concentrator solar cell prototype with a heat sink fabricated based on the simulation optimized structure is built. Outdoor temperatures of the prototype are tested. Temperatures of the solar cell and heat sink are stabilized with time continuing at about 37 ℃-38 ℃ and 35 ℃-36 ℃respectively, slightly lower than the simulation results because of effects of the wind and cloud. Thus the simulation model enables to predict the thermal performance of the system, and the simulation results can be a reference for designing heat sinks in the field of single concentrator solar cells.