Small Temperature Difference Research Articles

Structural selection of liquid hydrogen lubricated herringbone spiral-grooved thrust bearing considering viscous dissipative heat

Spiral-grooved thrust bearing (SGTB) is one of the important kinds of supporting component in high-speed rotating devices. The high shearing rate of SGTB can produce a large amount of viscous dissipative heat, which causes a temperature rise. Dynamic pressure effect induces pressure variation in the herringbone SGTB (HSGTB). When liquid hydrogen (LH2) is used as a lubricant, cavitation caused by lower pressure and higher temperature can result in lubrication failure. Especially, the cavitation of LH2 is more prone to occur because of its small temperature difference between the triple point and critical point, and the smaller supercooling degree. The influence of thermal properties on the phase transition process of LH2 is more significant. In this paper, the thermal and mechanical performance of three different structures of LH2 lubricated SGTB is compared by considering viscous dissipative heat. Herringbone SGTB is proposed for better performance and feasibility of its application in LH2 lubrication. The static performances of HSGTB such as load capacity, friction torque, cavitation rate, average temperature, and heat flux have been evaluated numerically by introducing the cryogenic cavitation model. The orthogonal sampling method and range analysis are used to optimize the HSGTB structure. Compared with the original HSGTB, cavitation rate and temperature rise are significantly suppressed in the optimized HSGTB. In addition, the load capacity is also improved effectively at high rotational speed, which is expected to be applied to high-speed centrifugal pumps.

Comprehensive performance analysis of cold storage Rankine Carnot batteries: Energy, exergy, economic, and environmental perspectives

Rankine Carnot batteries have demonstrated promise as a viable solution for electricity storage due to their high energy density at low temperatures. A specific variant of these batteries, known as the Cold Storage Rankine Carnot Battery (CSRCB), utilizes a vapor compression refrigeration (VCR) unit to store cold energy at sub-ambient temperatures. In this paper, three different configurations of CSRCB are constructed: the Basic CSRCB (B-CSRCB), CSRCB with a recuperator in VCR (R-CSRCB), and CSRCB with a recuperator in VCR and a preheater in ORC (RP-CSRCB). The system is analyzed from four perspectives: energy, exergy, economic, and environmental (4E). The impact of key parameters, such as heat source temperature, ambient temperature, and pinch point temperature, on the system's performance is evaluated. The results indicate that the RP-CSCBR configuration outperforms others in terms of energy, exergy, and economic analysis. The evaporator in ORC-subsystem is the component with the largest exergy loss. When the three configurations of CSRCB achieve the maximum exergy efficiency under different conditions, the ORC-subsystem evaporator accounts for 41.9 %, 41.9 % and 17.6 % of the exergy loss of B-CSRCB, R-CSRCB and RP-CSRCB, respectively. The lowest levelized cost of storage (LCOS) can be obtained when the system is operating at high heat source temperature, low ambient temperature and small pinch temperature difference. The environment assessment results show that the changes of the key parameters of the system have different effects on the annual emission reduction (AER) and total equivalent warming impact (TEWI) of CSRCB with different configurations.

Comparative analysis and optimization of waste-heat recovery systems with large-temperature-gradient heat transfer

Efficient utilization of waste heat is crucial for reducing waste heat emissions and minimizing environmental impact. Organic Rankine cycle (ORC) systems are commonly employed for waste heat recovery. However, conventional ORC systems have limitations in effectively harnessing waste heat resources because of differences in the pinch point temperature and the relatively small temperature difference between the heat source inlet and outlet. To address this issue, we designed two absorption organic Rankine cycle (AORC) systems in this study based on absorption heat exchangers. We analyzed the energy, exergy, and economy of three ORC system models with heat source temperatures within the range from 363.15 K to 413.15 K. The results indicated that the AORC system represented a optimal waste heat recovery system, capable of reducing the outlet temperature to 298.70 K and achieving a high temperature efficiency of 1.037. Thus, an AORC system can facilitate heat exchange with substantial temperature differences, enabling the efficient utilization of heat sources. The AORC system in this study exhibited a high net power of up to 151.8 kW, and an electrical exergy efficiency of 55.45%. Additionally, the AORC consistently outperformed other systems in terms of economy, as evidenced by its electricity production cost, which was the lowest among all three systems with heat source temperatures lower than 398.15 K.

Effect of hydrodynamic slip on thermoelectric response in negatively-charged nanofluidic channels

Nanofluidic thermoelectrics has attracted significant interest recently due to its potential for low-grade heat recovery. However, the impact of hydrodynamic slippage on power generation performance in nanofluidic channels has generally been ignored in previous studies, although slip velocity boundary conditions are relevant at the nanoscale. To fill this research gap, this study conducted two-dimensional (2D) numerical simulations based on non-isothermal Poisson, Nernst–Planck, Navier–Stokes, and energy equations to investigate the thermoelectric response, including Seebeck coefficient, thermoelectric current, power factor, and normalized maximum power density, within a nanochannel with slippage at the channel walls. The simulations considered three thermal-driven ion transport mechanisms: temperature-dependent ion electrophoretic mobility (TDIEM), Soret-type ion thermodiffusion, and thermoosmosis. The results showed that TDIEM and thermoosmosis primarily dominate the thermoelectric response of electrolyte confined in slip nanochannels in the presence of the overlapping electrical double layer. The study also found that the impact of access resistance on the thermoelectric response must be considered. The slip-enhancement of the Seebeck coefficient, i.e., the thermoelectric voltage at open-circuit condition, is not significant due to the increase in surface conductivity caused by slip-amplified electroosmosis, especially at low electrolyte concentrations. However, slip-amplified thermoosmosis greatly enhances the thermoelectric current at short-circuit condition, in the absence of the access resistance effect, leading to a significant improvement in the performance of ionic thermoelectricity in nanochannels with hydrodynamic slippage. At a moderate slip length ranging from 10 to 50 nm, it was found that the normalized maximum power density in a 2 nm nanochannel exceeded 10 mW K−2 m−2, even under a small temperature difference of 10 K, which is one order of magnitude higher than the typical thermionic capacitors and thermocells. Overall, this study provides valuable insights into developing efficient nanofluidic-based thermoelectric generators for low-grade heat energy harvesting by highlighting the importance of considering the effect of hydrodynamic slippage.

Bacterial populations in different parts of domestic drinking water systems are distinct and adapted to the given ambient temperatures

Drinking water enters buildings with a given microbiological community composition. Within premise plumbing systems, the drinking water is subject to very different conditions and temperatures. Whereas part of the water stays cold, another part is heated to provide hot water. In this study, drinking water samples were taken at different locations in four buildings that had central heating circles and that were equipped with ultrafiltration modules. The latter were intended to keep bacterial numbers low. When studying the increase in bacterial concentrations in these water samples using regrowth tests at different incubation temperatures, a temperature-dependence could be observed. Bacteria in cold water samples propagated best when incubated at 22°C, but often poorly at 36°C and not at all at 50°C. Bacteria in hot water samples showed the reverse behavior and grew best when incubated at 50°C, whereas growth at 22°C was poor or associated with a long growth lag. Water samples from distal taps in periphery locations used for retrieving both cold and hot water showed intermediate growth behaviors. Results suggest the existence of different temperature-adapted bacterial populations within domestic drinking water systems. The finding was supported by sequence data revealing distinct differences in the microbiomes between cold and hot water samples. Abundant bacterial groups in hot water included Deinococci, Kryptonia, Ignavibacteria, Nitrospiria, Gemmatimonadetes and different genera of Gammaproteobacteria. Stagnation of hot water at 50°C, 55°C, or 60°C furthermore shaped the microbiome in different ways indicating that small temperature differences can have a substantial impact on the bacterial communities.

Effect of Ag addition on the oxidation behavior of CrAlN coating at elevated temperatures

The effect of oxidation temperature and amount of Ag addition on CrAlN coating was investigated in this study. No Ag and Ag-based CrAlN coatings were deposited on a substrate using a physical vapor deposition (PVD) technique. The coatings then were isothermally heated at 800 °C and 900 °C for the 2 hr. Interestingly it is found that even with a small difference in temperature (100 °C), CrAlNAg coating shows different nature of oxidation, mass gain curve, coating microstructure and surface morphology.Surface morphology revels the Ag clusters formation on the top associated with the high temperature heating. While cross-section morphology gives information about Ag distribution and oxides layer formation. Mass gain curve and EDS (Energy-dispersive X-ray spectroscopy) results revealed that the oxidation resistant behavior of the CrAlN coating was degrade with increasing Ag content and/or increasing oxidation temperature. Overall, the results suggest that the temperature has a significant effect on the microstructure and properties of Ag-based coatings, and optimizing the deposition temperature can improve the performance of these coatings in various applications.

Thermo-hydraulic rating of a gasketed-plate heat exchanger for methanol heating

The use of plate heat exchangers is desirable since they have a simple compact construction, are reliable, and very efficient at small temperature difference between fluids. In the present work the thermo-hydraulic rating of a proposed gasketed-plate heat exchanger was carried out, in order to heat a methanol stream. A safety factor of 1.62, a percent over surface of 3.91% and a cleanliness factor of 0.962 was obtained. The calculated values of the pressure drops for both the hot water and methanol streams were 47,199.05 Pa and 78,414.61 Pa, respectively, while the pumping power required for those both streams were 4.81 kW and 11.38 kW, respectively. The proposed gasketed-plate heat exchanger can be used for the requested heat transfer service since the percent over surface is lower than 25% and the calculated pressure drop of both streams are below the maximum permissible pressure drop established by the process.

Thermal performance analysis and burning questions of refrigerant direct cooling for electric vehicle battery

Refrigerant direct cooling technology has been gaining attention due to its advantages of simple system composition and high cooling efficiency, but its temperature control performance does not have advantages over mature liquid cooling in industrial applications, reasons for which should be discovered. This paper proposes a novel discrete model based on an electro-thermal coupling method and thermal resistance network to analyze the local temperature control performance of refrigerant direct cooling and liquid cooling systems under real operating scenarios with acceptable computing time and accuracy. The results show that the phase change of the refrigerant in the refrigerant direct cooling plate significantly affects the temperature control performance. The vapour-liquid two-phase zone has a high heat transfer capability, which can dissipate heat well and maintain a small temperature difference with the maximum temperature of the battery reduced by 28.3% compared with the liquid cooling system. There is a serious heat transfer deterioration in the superheated gaseous zone, causing a significant increase in the local battery temperature, and the maximum temperature difference is much higher than that in the liquid cooling system. When the refrigerant switches from two-phase to single-phase under 2C charging condition, the heat transfer coefficient reduces by roughly 73.6%, which causes the accompanying battery unit temperature to rise by about 12 ∼ 14 °C. Besides, the low refrigerant temperature will cause a large temperature difference in the vertical direction of the battery, which restricts the application of the refrigerant direct cooling system in practice. When the evaporation pressure increases from 300 kPa to 500 kPa, the temperature difference will decrease from 14.1 °C to 8.8 °C which is a 37.6% reduction. Through an in-depth analysis of the local temperature distribution of battery units, two burning questions were identified which deteriorate the temperature control performance of the refrigerant direct cooling system and results can provide directions for performance improvement.

THERMODYNAMICS ANALYSIS OF SOLAR-EJECTOR PUMP OTEC (SEP-OTEC) RANKINE CYCLE USING AMMONIA AS REFRIGERANT

Organic Rankine Cycle (ORC) applications include ocean thermal energy conversion (OTEC), in which mechanical work is generated from heat energy to rotate generators and generate electricity. The OTEC system heated and cooled its refrigerant by taking advantage of the relatively small temperature difference between the warmer surface seawater and the colder deep seawater. The low-temperature difference between seawater and the rest of the system meant that the thermal efficiency of the system was relatively low; to address this problem, the OTEC cycles needed to be revised. To increase the basic OTEC cycle's thermal efficiency by 3.3–4.0%, various modifications have been developed. Two such cycles are the Solar Boosted OTEC (SOTEC) cycle and the Ejector Pump cycle (EP-OTEC). While the two improvements alter the rotating turbine parameters in different ways, they can be combined to create an improved OTEC cycle through the use of thermodynamics. In this study, an algorithm for revised OTEC was developed using MATLAB, and the performance of the system after the modifications was further quantified. This SEP-OTEC cycle thermal efficiency gives a 1.2-fold improvement when compared to the previous OTEC cycle thermal efficiency, which was 3.1%.

Control of stress distribution during large radius fiber optic taper drawing process based on 2D simulation

This paper presents numerical investigation of stress distribution within fiber optic taper during its drawing process. A thermoviscoelastic model is proposed to describe the glass mechanical behavior from solid to liquid in a broad temperature range where the fiber optic taper drawing undergoes. The model is validated by experiments and used to study stress distribution in the fiber optic taper during fabrication. Roles of key parameters are discussed including geometrical configuration of the furnace, temperature difference between heating and cooling regions and drawing speed. Results show that the stress distribution is mainly influenced by thermal environment surrounding the taper. While the afore-mentioned key parameters all affect the thermal environment, they thus also change the stress distribution in the fiber optic taper. A shorter length of adiabatic region and smaller temperature difference between the heating region and cooling region make the impact of cooling region on thermal environment to fiber drawing more significantly. Conversely, a longer adiabatic region and a larger temperature difference will enhance the impact of heating region. Proper increase in drawing speed can promote heat transfer arising from rheologic motion, thus improving the homogeneity of stress distribution in the fiber taper. Based on the understanding derived from this study, an improved heating and drawing design is proposed to achieve more homogeneity of stress in fiber optic taper during the drawing process.

Effect of thermal capacitance on microchannel heat sink response to pressure drop oscillations

The efficient heat transfer resulting from flow boiling in microchannel heat sinks can help dissipate high heat fluxes from high-density electronic devices across a small temperature difference. However, practical implementation challenges unique to two-phase flow boiling, as compared to single-phase liquid cooling, have prevented its widespread adoption. A primary challenge is the occurrence of dynamic two-phase flow instabilities, such as pressure drop oscillations (PDO), that have the potential to degrade heat transfer performance or trigger premature critical heat flux (CHF) under some conditions. Under other conditions, PDOs are observed to have little to no impact on performance. One factor proposed by modeling studies to be responsible for this discrepancy in observations of the effect of dynamic instabilities on performance is the thermal capacitance of the heat sink, though this has not been confirmed by experiments. In this study, the effect of thermal capacitance on the transient thermal response of a heat sink experiencing PDOs is examined through use of a dynamic two-phase flow model and experiments. Flow boiling experiments are performed with a controlled compressible volume upstream of parallel-microchannel heat sinks having either a large or a small thermal capacitance. In accordance with the behavior predicted by our model, when thermal capacitance is reduced, the pressure drop oscillation frequency is found to decrease and temperature swings in the heat sink become more severe. Additionally, the experimentally measured CHF limit is diminished in the heat sink at smaller thermal capacitance. These results reveal thermal capacitance as a critical parameter that determines how much dynamic instabilities degrade flow boiling performance in a microchannel heat sink.

Thermoelectric Properties of the Corbino Disk in Graphene.

Thermopower and the Lorentz number for an edge-free (Corbino) graphene disk in the quantum Hall regime is calculated within the Landauer-Büttiker formalism. By varying the electrochemical potential, we find that amplitude of the Seebeck coefficient follows a modified Goldsmid-Sharp relation, with the energy gap defined by the interval between the zero and the first Landau levels in bulk graphene. An analogous relation for the Lorentz number is also determined. Thus, these thermoelectric properties are solely defined by the magnetic field, the temperature, the Fermi velocity in graphene, and fundamental constants including the electron charge, the Planck and Boltzmann constants, being independent of the geometric dimensions of the system. This suggests that the Corbino disk in graphene may operate as a thermoelectric thermometer, allowing to measure small temperature differences between two reservoirs, if the mean temperature magnetic field are known.

Simultaneous measurement of normal spectral emissivity and temperature of materials with low thermal conductivity

This study develops a measurement system and a method for measuring the normal spectral emissivity and temperature of low thermal conductivity materials at high temperatures. A self-design heating device using a synergistic heating treatment including a high-power laser and a radiation heating cavity is introduced, and a Fourier transform infrared spectrometer is utilized to measure the radiation signal of sample. Based on the temperature hypothesis model, which considers normal spectral emissivity keeps constant within small temperature difference less than 10.0 K, a method is proposed for realizing the inversion of normal spectral emissivity and temperature with the multispectral radiation signal. A genetic algorithm-based technique with big mutations is used to estimate the normal spectral emissivity and temperature of sample at high temperatures. The variation of blackbody radiation signals with the blackbody radiance is analyzed to verify the linearity for the detector of FTIR spectrometer. The apparent normal spectral emissivity of an alumina ceramic fiber is determined in the spectral range of 2.5–25.0 μm at 673–1273 K. Furthermore, the uniformity of temperature distribution on the sample surface and inside the sample is numerically evaluated. The standard uncertainty in the experiment at 1273 K is less than 4.0 % in the investigated bands.

Flexible Active Peltier Coolers Based on Interconnected Magnetic Nanowire Networks.

Thermoelectric energy conversion based on flexible materials has great potential for applications in the fields of low-power heat harvesting and solid-state cooling. Here, we show that three-dimensional networks of interconnected ferromagnetic metal nanowires embedded in a polymer film are effective flexible materials as active Peltier coolers. Thermocouples based on Co-Fe nanowires exhibit much higher power factors and thermal conductivities near room temperature than other existing flexible thermoelectric systems, with a power factor for Co-Fe nanowire-based thermocouples of about 4.7 mW/K2m at room temperature. The effective thermal conductance of our device can be strongly and rapidly increased by active Peltier-induced heat flow, especially for small temperature differences. Our investigation represents a significant advance in the fabrication of lightweight flexible thermoelectric devices, and it offers great potential for the dynamic thermal management of hot spots on complex surfaces.

Effects of Temperature Difference and Heat Loss on Oscillation Characteristics of Thermo-Solutocapillary Convection in Toluene/N-Hexane Mixed Solution

During the crystal growth process using the floating zone method, the uneven distribution of impurities on the surface of the melt can trigger a coupling mechanism between solutocapillary convection driven by the concentration gradient and thermocapillary convection driven by the temperature gradient, resulting in the Marangoni convection at the free surface. When the temperature and concentration gradients reach certain values, the crystal surface and interior exhibit time-dependent, periodic oscillations, leading to the formation of micrometer-scale impurity stripes within the crystal. This study focuses on the effects of temperature difference and heat loss in a liquid bridge under microgravity on the structure and interface oscillation characteristics of thermo-solutocapillary convection, aiming to explore the coupling phenomenon of this oscillation and provide valuable information for crystal growth processes. An improved level set method is employed to accurately track every displacement of the interface, while the surface tension is addressed using the CSF model. In addition, the area compensation method is used to maintain simulation quality balance. A comprehensive analysis is performed on the oscillation characteristics of thermo-solutocapillary convection at the free surface, ranging from the temperature, concentration, deformation, and velocity distributions at the upper and middle heights of the liquid bridge. The results indicate that under small temperature differences (ΔT = 1 − 3), the transverse velocity at the upper end exhibits a single-periodic oscillation, while the longitudinal velocity presents a double-periodic oscillation. At the intermediate height, both the transverse and longitudinal velocities display a single-periodic oscillation. Under a large temperature difference (ΔT = 6), the oscillation of velocities at the upper end and the middle position become multi-periodic. In addition, heat loss has certain regular effects on the oscillatory flow of thermo-solutocapillary convection within a certain range. The velocity, amplitude, and frequency of the upper end and the middle position at the free surface decrease gradually, and the oscillation intensity also weakens with the increase in heat loss (Bi = 0.2 − 0.6). These new discoveries can provide a valuable reference for optimizing the crystal growth process, thereby enhancing the quality and performance of crystal materials.

Polarization Snapshot Imaging Spectrometer for Infrared Range

Infrared imaging spectrometers detect and identify targets by collecting spectral and image information. However, when detecting small temperature differences and dynamic targets, the accuracy of infrared detection is reduced, the traditional scanning structure detection time is longer, the real-time performance is poor and it is easy to introduce motion artifacts. This paper proposes an infrared polarization snapshot spectral imaging system (PSIFTIS) based on a polarizer array, a lens array and a roof-shaped stepped micromirror. Polarized light can solve the problem of small-temperature-difference target recognition by characterizing the surface properties of materials. Lens arrays utilize multi-aperture imaging to achieve snapshot detection of targets. The system can obtain 4D data information, including polarization, in a single measurement cycle. This study completed the overall optical design of a PSIFTIS and an optical simulation experiment using it. Finally, a system prototype was built in the laboratory and a polarization spectrum detection experiment was carried out. The experimental results show that the PSIFTIS could accurately obtain the polarization spectrum information for the target, the spectral resolution reached 7.8 cm−1 and the Stokes measurement error was less than 5%.

Numerical investigation of bed-to-tube heat transfer in a shallow fluidized bed containing mixed-size particles

Mixed-size particles with low processing cost have great potential to act as the absorbing media in the next-generation concentrated solar power plants. However, the research on the heat transfer from the particles to heated surfaces in gas–solid fluidized beds is limited. In this paper, the bed-to-tube heat transfer coefficient (HTC) in a shallow fluidized bed with immersed tubes is determined numerically. The Eulerian–Eulerian approach that incorporated the kinetic theory of granular flow has been implemented in a two-dimensional model. The distribution of the local HTC around the tube is investigated for various particle systems. The results show that the HTC reaches a maximum at the upper right (45°) and upper left (135°) of the tube, respectively, indicating a strong relation between the local HTC and solid volume fraction (SVF). The average HTC increases as the mean particle size gets smaller. For monosized particles, the HTC increases from 925 W/(m2·K) to 3033 W/(m2·K) as the particle size decreases from 300 to 100 µm. For binary particles, the growth in the HTC is nonlinear, with an increase in growth rate being observed as the small-size component becomes dominant. For mixed-size particles with the same mean size, a higher HTC can be achieved by enlarging the size difference between the components. A modified correlation for predicting the bed-to-tube HTC is established. Besides, the impacts of gas velocity and temperature, and heat radiation on the bed-to-tube HTC are discussed. It is found that an optimal gas velocity exists to maximize the average HTC and SVF simultaneously, while the gas temperature has a minor contribution. Due to the small heat transfer temperature difference, the effect of thermal radiation on the HTC can be neglected even though the bed temperature reaches 800 °C.

Cryogenic Thermomechanical Compressor

The purpose of this work is to create a compact supercharger to provide circulation of protective gas medium in a closed circuit. It was proposed to use a thermomechanical compressor to achieve this purpose. The operating principle of such devices is to change cyclically the temperature of the working medium in contact with warm and cold sources. Heating and cooling are carried out sequentially, pushing a part of gas through the regenerator by means of a displacer. The energy consumption for piston displacement is lower by an order of magnitude than that in conventional compressors. This makes it possible to use a seamless displacer movement mechanism. There can be two designs, both with one of the heat carriers close to ambient temperature. In a high-temperature thermomechanical compressor, the temperature is usually does not exceed 800 K. In the second type compressor, by reducing the absolute temperature of the cold "source" it is possible to achieve a high degree of compression at a relatively small temperature difference. The most significant result of the work is the design of the small-sized thermos-compressor that ensures a moderate degree of gas compression. The significance of the achieved results is shown in the compactness and tightness of the prototype for the use as an alternative to traditional machines in the field of inert gases production. The proposed technical solutions were tested during bench tests of the thermomechanical compressor. The experimental dependences were obtained of the flow rate characteristics on temperature mode, discharge pressure and cycle period.

Investigation of the Effective Voltage and Performance of Thermocells

Thermocells, also called thermogalvanic cells, are a promising technology that can efficiently harvest low-grade waste heat with direct thermoelectric conversion. The cells operate under a temperature difference, with one electrode on the hot side and the other on the cold side. The recently developed electrodes, such as porous carbon materials and pin-structured electrodes, have led to a temperature gradient even inside one of the electrodes. However, it still remains an open question of what temperature difference determines the open-circuit voltage of thermocells. Here, we investigated the effective voltage of a thermocell with thick electrodes. The temperature difference that determines the voltage turned out to be the smallest temperature difference between anode and cathode electrodes, the average temperature difference, or in between, depending on the internal resistances of the cell. We also verified the validity of normalized power density estimated from the open-circuit voltage. In addition, a strategy was demonstrated to improve the power density of a thermocell that consists of thick electrodes. The results provided here would help devise high-performance thermocells with optimized electrode structures.

Dynamic thermal responses and showering thermal comfort under different conditions

This study conducted a series of human subject experiments on shower thermal comfort to investigate the dynamic thermal responses under different conditions. Questionnaires (including thermal sensation votes, thermal comfort votes, sweating sensation votes, and mood-related votes) and physiological parameters (including skin temperature, core temperature, heart rate, blood pressure, and brain waves) were collected from 27 subjects. The results showed that the subjects’ comfort-related votes changed dynamically during the pre-, mid-, and post-showering phases. The changes in thermal sensation, thermal comfort, fatigue relieving, and sweating sensation during the 10-min shower were 0.7 ± 0.8, 0.9 ± 1.2, 0.9 ± 1.0, and 0.9 ± 0.9, respectively. After a 10-min shower, 16 mood-related questions were answered toward positively. The heart rate and mean skin temperature of the subjects increased by approximately 10% and 8%, respectively. The body temperature tended to be more uniform, with smaller temperature differences between the trunk and extremities. The changes in core temperature, blood pressure, and brain waves were less significant because the reference test condition (25 °C air temperature, 40 °C showering water temperature, and 10-min duration) was not intensive. Further analyses indicated showering water temperature and duration were the most significant factors affecting the mid-showering thermal comfort. The ambient temperature and airspeed were the most significant factors affecting post-showering thermal comfort. The initial thermal status primarily affects thermal comfort before showering. No significant difference was observed between the elder and the younger subjects under moderate conditions.