Temperature Side Research Articles

Performance of hybrid vaccine freezer that combined thermoelectric coolers with vapor compression refrigeration: Experimental assessment

AbstractIn the medical field, refrigeration systems are used to store and transport vaccines, blood, and other medical supplies that require specific temperature ranges to remain effective. As technology continues to advance, the demand for more efficient and sustainable refrigeration systems is also increasing. The freezer compartment is typically designed to maintain a temperature of −18°C to −23°C for storing frozen items. Consequently, this work aims to develop a hybrid refrigeration system that combines a thermoelectric cooler system (TEC) and a vapor compression refrigeration cycle (VCC) system to achieve lower temperatures than conventional refrigerators. Also, the performance of the proposed hybrid refrigeration system is experimentally assessed with various operating conditions, including varying the voltage delivered to the system. The experimental results exhibited that the temperature inside the freezer room reached −33°C, while the cold side temperature is −47°C. Also, the maximum coefficient of performance of the VCC system, TEC, and hybrid system is 2.07, 1.06, and 0.37, respectively, at a DC voltage applied of 6 V. Moreover, the results revealed that the hybrid system combining a TEC and a VCC system can be a valuable technology for specific applications with low temperatures and limited capacity requirements.

The effect of the glass planes on thermal comfort in office buildings: a case study

One of the most important aspect in architecture is the selection of exterior material. This materialsurface faces directly with building’s surrounding climate and environment, transferring the heat through its wall and roof significantly so it requires more consideration from the planners. Widely use of glasses as building’s exterior impacts its heat absorbing thereby it needs more power for air conditioning in order to keep the interior temperature productively workable. The objective of this research is to observe the impact between glass partition and interior thermal condition, how the habitants react, and also the ideal temperature for both users and building’s OTTV. Correlational research combines results from thermal observation and user’s perceptionin order to get its convenience thermal condition and to know its OTTV so we can issue the standard

Investigation of the performance enhancement of building-integrated photovoltaic system using evaporative porous clay applied in different building's directions

The integration of photovoltaic (PV) modules with building's facades and roofs results in significant reduction in the PV module's efficiency owing to its temperature rising, as well as increasing in the building's indoor thermal gain. Thus, this study proposed cost-effective and eco-friendly passive cooling technique utilizing evaporative porous clay material to minimize the integrated PV module's temperature. An experimentally validated numerical study is being performed using different clay thickness and porosity to estimate the expected enhancement in the thermal and electrical performance of the building-integrated photovoltaic (BIPV) system. The experimental tests were carried out using prototype of small rooms integrated with PV panels installed with a water-saturated porous clay material to validate the presented transient numerical heat and mass transfer model. After that, the proposed system is being compared with another passive cooling mechanism using phase change material (PCM), and the results are then analyzed and compared. The findings showed a maximum reduction of 19.1 °C and 12.8 °C of peak PV temperature when the porous clay and PCM are utilized, while the building's side temperature reduced by around 11.2 °C and 10.9 °C, respectively. Further, porous clay achieved up to 9.8 % improvement in PV system's efficiency, with a maximum water consumption rate reached around 3.35 L/h.m2. Moreover, applying such a porous clay cooling approach resulted in a maximum reduction of 53.8 % in the building's annual thermal load. In the outcomes reported here, porous clay with the least thickness and highest porosity achieved more feasible cooling effects compared with PCM.

Temperature Condition Analysis for Freezing on Tunnel Lining Back Side According to Tunnel Length

Railway mountain tunnels were constructed in cold regions of Korea recently, and freezing has been generated. Most mountainous railway tunnels are designed with waterproofing membranes since groundwater exists on the backside of the tunnels. The lower air temperature inside the tunnel is transferred to the back of the tunnel lining as the outside air temperature drops below zero in winter, causing the groundwater behind the waterproofing membrane to freeze. There have been cases of freezing-related damage, such as the obstruction of drainage flow and freezing groundwater leakage. Therefore, the freezing conditions inside the tunnel should be analyzed by each tunnel length after the air temperature variation in the tunnel is measured. In this study, the air temperature inside a railway tunnel located in a cold region was measured using thermometers. The inside air temperature over time was changed by the DTR (diurnal temperature range) every 24 h. The DTR inside the tunnel was also reduced far from the entrance. Heat transfer analysis was implemented considering the air temperature variation inside the tunnel. Assuming that the minimum air temperature freezing inside the tunnel lasts seven days, the higher the minimum air temperature the longer the tunnel length. The research results show that the freezing inside a tunnel can be estimated from the tunnel length and the minimum air temperature inside the tunnel.

Studying the Role of Workplaces Layout on Employees Health: Sick Building Syndrome

Background and Objectives: Workplace architecture is one of the most important factors influencing employees' health and wellbeing. Therefore, it is necessary to study the role of workplace design on the emergence of various types of health problems among employees. The present research aims to study the prevailing conditions at the case studied workplaces and to identify the role of factors influenced by interior layout (location-ergonomics, lighting, indoor air quality (IAQ), temperature, noise, design style, and cleaning) on the emergence of Sick Building Syndrome among employees.
 Methods: In the present study, three administration buildings (roads and urban development office, construction engineering organization, and airport) in Urmia, Tabriz are investigated as case studies and a total of 226 employees working in these buildings are selected as samples. Then, they are asked to fill out a questionnaire to collect the required data. The reliability of the questionnaire is confirmed using Cronbach's alpha coefficient.
 Results: The findings indicate that despite the advantages of open plan layout for the organization of work environments, it still has many negative consequences such as too much noise and distraction, lack of ergonomics, congestion, reduced privacy, and the lack of personal control of environmental conditions. In general, it is not considered an efficient layout design for the workplace.
 Conclusion: The results indicate that to effectively deal with the emergence of sick building syndrome and provide a healthy work environment, it is necessary to establish a balance between various parts in the workplace layout design including private office space, shared workplace, and/or open plan according to the nature and type of work while taking into account the factors and parameters influenced by the layout design and environmental properties.

Mathematical Modeling and Validation of Solar-Induced Ventilation System for Vehicle Cabin Cooling in Hot Parking Conditions

Exposure to direct sunlight raises interior temperatures in vehicle cabins, risking heat-related illnesses. Solar passive techniques mitigate this issue, especially during hot parking conditions. However, a comprehensive mathematical model encompassing both solar chimney and vehicle cabin is lacking. This study develops a novel mathematical model to predict temperature distribution and airflow rate, enhancing system performance evaluation. The system comprises a solar air collector with an adjustable arm mounted on the vehicle's roof. The model was validated theoretically and experimentally. The experimental work is conducted with the physical model with an air gap of 0.1 m, 0.77 m width, and a 1.12 m collector length under outdoor conditions. Results indicated a gradual increase in temperatures of the glass cover, air in the collector channel, absorber, and mass airflow rate with solar radiation intensity, significantly influencing system performance. The high value of R2 and the consistency of the model's results with theoretical and experimental outcomes justified the validity and accuracy of the proposed model, exhibiting a deviation percentage of less than 10%. The developed model can be utilized to study influential parameters for optimizing the proposed strategy's performance and components, yielding comparable results to experimental data. Additionally, it provides researchers and car makers with a broader perspective and a range of options for further improvement in weight, size, cost, and aerodynamic of the vehicle.

Physicochemical Quality of Oyster Mushroom for Functional Food

This article presents studies on the physicochemical quality of oyster mushrooms grown within a housing and controlled by the Internet of Things (IoT). The goals of this study were to assess (1) the impact of indoor air quality on the growth and quality of mushrooms and (2) the antioxidant content of oyster mushrooms. In this study, the air temperature and humidity of oyster mushroom house per unit time was recorded and controlled automatically by an IoT system. Additionally, their physicochemical and microbiological quality were evaluated using physico-analytical instruments, and the potency of their ergothioneine (EGT) content was investigated using the HPLC method. The temperature of the air inside was between 29 and 35 °C, and the relative humidity was between 60% and 90%. The average texture of mushroom is soft. The average length, width, and height of the fresh mushroom were 41.5 mm, 60.0 mm, and 29.5 mm, respectively. The microbiological test confirmed that there was no salmonella infection in the collected mushrooms. The button-stage mushrooms have less total fungus than the bloom-stage mushrooms. The extraction standard method employs an EGT content of 0.674 mg/g as determined by chromatography data analysis. The oyster mushrooms can be consumed as a healthy meal, and the study of EGT showed also very prospective as one of immunotherapeutic food. Keywords: Ergothioneine, Fibre-reinforced plastic house, Internet of think, Oyster mushrooms

Modeling and Simulation Analysis of Operation Characteristics of Supplemental Fired Absorption Heat Exchanger

Based on a general single-segment absorption heat exchange unit, a series complementary lithium bromide absorption heat exchange unit was constructed by adding a direct combustion unit, which can achieve a lower backwater temperature on the primary side, thereby increasing the heating capacity. Based on the analysis of the thermodynamic cycle and heat-transfer process, the mathematical model was built and solved using an iterative numerical method. Based on satisfying heating load, the impact of the temperature of supply water on the primary side on the operating characteristics of the unit under different load conditions was quantitatively analyzed. The result shows a negative correlation between backwater temperature on the primary side and supply water temperature on the primary side when other parameters are unchanged. If the supply water temperature on the primary side remains unchanged, the temperature of the backwater on the primary side decreases with the increase of heating load, and the ratio of heat exchange of plate heat exchange unit to total heat exchange decreases with the increase of heating load. For example, when the supply water temperature is 120°C, the proportion of water-water plate heat exchange capacity to total corresponding to 100% heat load, 90% heat load, and 75% heat load is 0.465, 0.580, and 0.772, respectively.

Experimental study of micro-encapsulated phase change materials’ influence on indoor temperature

The energy use of buildings is almost one-third of the global final energy use. Phase change Materials (PCMs) are substances that undergo phase transition when the surrounding temperature reaches their phase transition temperature. PCMs are reported to be a good candidate as a thermal storage buffer in building systems. Accordingly, PCMs may be able to regulate the indoor temperature while using less energy and thereby contributing in improving the energy performance of the building. In this project a trail to analyse the effect of PCMs in indoor temperature was carried out, in an experimental set-up, using a climate chamber. The chamber temperature is regulated as a sinusoidal profile with a cycle of 24 hours, with a maximum of 40 °C and a minimum of -10 °C. A cubic-box, is placed at the centre of the chamber, and is used as a representation of “building”. A board was made by encapsulating PCMs, with a melting temperature of 24 °C, to gypsum with a fraction of 20 wt%. The influence of PCM added gypsum board on inside temperature of the box is studied. Temperatures at different locations have been measured by thermocouples. The results indicated that the presence of PCM resulted in less temperature variation inside the box with the temperature holding close to the PCM transition temperature for a long period. Also, the PCM boards shifted the temperature profile. Further results are expected to determine the location of the PCM board that is most suitable to reduce the temperature variation inside the building.

Investigation of Performance Estimation Methods Validity of Thermoelectric Module

The thermoelectric cooling system is now widely used in small-capacity applications. This system is designed to remove the heat by using a thermoelectric module thus the selected object can be maintained at the required range of temperature. The performance of the thermoelectric module system can be estimated by using the information from the technical datasheet issued by the manufacturer. Two commonly used methods for estimating the cooling capacity of the system are performance curve and energy balance. This study aims to investigate the accuracy of those two methods compared with the experimental results. The experiment was performed by maintaining the hot side temperature at 50 °C. To estimate the cooling capacity, the heat conduction on the stainless-steel block was calculated. The results showed the estimated cooling capacity of the thermoelectric system was up to 48% and 10.1% higher than the experimental result by using energy balance and performance curve methods, respectively. It implied that the performance curve method is more accurate than the energy balance method.

Experiments and CFD simulation of an air-conditioned tractor cabin for thermal comfort of tractor operators in Pakistan

Tractors are manufactured without air-conditioned cabins in Pakistan. This leads to thermal discomfort for tractor operators working under direct solar exposure. Therefore, this study aimed to design and install an air-conditioned cabin on a tractor. Experiments were undertaken to evaluate the installed cabin performance under two scenarios i.e., conventional (S–I) and enhanced (S-II) air distribution. Computational fluid dynamics (CFD) simulations were used to analyze airflow and calculate thermal comfort indices. The results showed that the air-conditioned cabin attained optimum thermal conditions under the enhanced air distribution scenario (S-II). In this scenario, the inside cabin temperature was an average of 27.4 °C, compared with 30.4 °C in S–I. The relative humidity remained similar in both scenarios, around 53 %. The temperature difference between the cabin and the ambient environment was 11.09 °C in S-II, aligning with the thermal comfort conditions outlined in ISO 14269–2. Furthermore, the CFD simulations showed a predicted mean vote (PMV) index of 0.61 and the percentage people dissatisfied (PPD) index of 26.5 %. These results also confirm the provision of optimum thermal conditions for operator inside the cabin. The simulations also demonstrated good agreement with experimental data, with a small difference in air temperature (2 °C) and relative humidity (5.8 %). In the light of these findings, this study recommends installation of air-conditioned cabin on tractors with enhanced air distribution (S-II) in Pakistan to improve thermal comfort of operators.

The Effects of AC Electric Field on Ice Nucleation in the Super‐Cooling of a Distilled Water

The effects of an AC electric field on ice nucleation temperature and nucleation rate were investigated by freezing distilled water while exposing it to varied AC electric field strengths and frequencies. To eliminate the influence of ion injections and electric field concentrations at a metal electrode surface on ice nucleation, distilled water filled in resin cuvettes are used as samples. The samples are exposed to AC electric field induced by parallel plate electrodes placed outside of the cuvettes. The cuvettes and parallel plate electrodes placed in a freezer with an inside temperature fixed at −15°C. The electric field strength in the sample is 2 or 7.5 kV/m and frequency varies from 50 Hz to 10 kHz. The ice nucleation temperature and the nucleation rate of distilled water increase with increasing the electric field strength and the frequency. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Ultrasonic measurement of temperature distributions in extreme environments: Electrical power plants testing in utility-scale steam generators

Thermal heterogeneities within energy conversion and storage, material processing, nuclear processes, aerospace, and military applications are often inaccessible to characterization by insertion sensors. When sensor deployment is possible, conventional pointwise temperature probes quickly degrade when inserted into harsh environments typical of such processes. We developed spatially-resolved ultrasonic thermometry to noninvasively measure the spatial distributions of thermal properties in such applications, even when sizable thermal gradients are present. Our method divides the path of ultrasonic propagation into segments bound by echogenic features, which create echoes in pulse-echo mode, encoding the information about interior temperature distributions. We use the acquired ultrasonic responses to estimate the internal temperature distributions by solving an inverse problem or concatenating segmental estimates. This work describes the implementation and industrial testing of the developed method at a coal-fired electrical power generation plant. We inserted an echogenically segmented Inconel 625 waveguide into the combustion zone of the utility-scale boiler and continuously acquired ultrasonic data while keeping sensitive components away from the damaging combustion environment. The accuracy of the time-dependent temperature distributions reconstructed from the ultrasonic measurements was comparable to that of thermocouples. The resiliency of ultrasonic thermometry to harsh combustion conditions was far superior to conventional insertion sensors. The measurements obtained during plant operation captured daily steam generation cycles in response to changing customer demand and intermittent contributions of renewable power sources to the power grid. These measurements have revealed new insights into the relationship between the dynamic power generation load and the conditions inside the steam generator. The successful industrial testing of spatially-resolved ultrasonic thermometry in solids indicates that the developed technology has matured to become an attractive alternative to conventional sensing in solving challenging problems of long-term thermal characterizations in extreme environments.

Optimized Thermoelectric Cooler Performance by the Structure-Matching Design of Asymmetrical p/n-Type Legs.

Commercial Bi2Te3-based thermoelectric (TE) coolers typically comprise equal-size p- and n-type legs. However, this traditional structure limits the cooling temperature differences of TE coolers (TECs) due to identical current density, when their electrical or thermal characteristics differ significantly. This work presents a novel design of p- and n-type TE legs to optimize the performance of TECs. The cooling properties of the materials are initially calculated by theoretical equations and then evaluated by using a combination of finite element simulations and experiments. The research findings suggest that by utilizing higher ZT p-type materials to enhance the TEC cooling performance, further optimization of the ratio of the cross-sectional area of the TE legs (Ap/An) improves the structural matching of the legs, which achieves the maximum figure of merit Z and leads to a 5.4% increase in cooling power density. Additionally, the TEC with optimized Ap/An increases the cooling temperature difference by 3.3 and 2.7 K for the same current at hot side temperatures of 300 and 315 K, respectively, while the coefficient of performance remains unchanged. Moreover, the maximum cooling temperature difference reaches 70 and 74 K, respectively. We anticipate that our results will guide the design and optimization of the TECs.

The energy efficiency and environmental analysis of open-type commercial display cabinet with a multi-flow air curtain design

Open vertical display case refrigerators are often preferred as commercial refrigerators. This is because, despite their high energy consumption they have a higher marketing potential with the product display and offer easy access. Commercial refrigeration system accounts for half of the energy consumption in supermarkets. Air curtains of different designs are used in open vertical cabinets to reduce heat and mass transfer between the cooled air and the indoor environment. Hence, an experimental study was conducted to evaluate the multi-flow designed air curtain effects on the energy efficiencies of open display case-type commercial refrigerators. The experiments were conducted with ISO 23953:2005 standard in a controlled test room. During the trials, four different temperatures of air flowed to the refrigerator: +25 °C, +11 °C, +2°C, and 0 °C respectively through the air curtains. As a result of the experiments, a higher Coefficient of Performance COP value and lower Energy Efficiency Index (EEI) value were obtained with multi-flow air curtains. The multi-flow designed air curtain has nearly 40 % eliminated the air entrained from the outside to the indoor environment. It has ensured that the interior temperature values remain at the desired level. The second polyurethane body has reduced heat transfer through the surface by about 30 %, thereby reducing cooling load and energy consumption.

Critical concentration effects of nanoparticle on combustion involved into secondary atomization and micro-explosion for B/JP-10/SP-80 nanofluid fuel

To increase the combustion heat of JP-10-based aviation fuel, boron nanoparticles (B NPs) and corresponding surfactant SP-80 was added into JP-10 to prepare the B/JP-10/SP-80 nanofluid fuel. However, critical concentrations of boron nanoparticle to influence the combustion performance involved into secondary atomization and micro-explosion have not been unveiled. This paper experimentally presented the combustion of B/JP-10/SP-80 nanofluid fuels containing the boron concentration of 0.25 ∼ 10.0 wt%. The combustion characteristics were achieved by investigating the combustion stages, effective burning rate, secondary atomization, micro-explosion, flame temperature, interior temperature of droplet, droplet lifetime, flame emission spectrum, morphology and size of the residues. Results show that at dilute concentrations the nanofluid fuels stably burned, and lastly took once micro-explosion till the depletion. While at dense concentrations, multiple secondary atomization and micro-explosions occurred during combustion. The critical nanoparticle concentration effect on the transition of combustion mode involved into secondary atomization and micro-explosion lies in the range of 2.5 ∼ 5.0 wt%, corresponding surfactant concentration of 1.25 ∼ 2.5 wt%. The addition of boron nanoparticle with high concentrations provides the porous / compact shell formed by boron agglomeration and melt bonding of B2O3 on the boron surface to promote the build-up and increment of pressure during the evaporation combustion of the JP-10, resulting in the occurrence of secondary atomization and micro-explosion. The secondary atomization and micro-explosion bring boron nanoparticles into the gaseous flame zone and to participate in the combustion, and thus much more combustion heat is released. The achieved combustion heat of boron nanoparticles feedbacks on the droplet, which increases the internal temperature of the droplet as well as the flame temperature. Although the effective burning rate of nanofluid fuel droplets decreased with the elevated boron concentration, the secondary atomization and micro-explosions greatly shortened the lifetime of the droplet by producing quantities of secondary droplets. The thermal feedback effect of the combustion flame was analyzed by coupling the flame temperature and the emission spectrum. Finally, the combustion routes involved into secondary atomization and micro-explosion were proposed to understand deeply the combustion behavior of B/JP-10/SP-80 nanofluid fuel.

Sterilization of oil palm fruit utilizing continuous microwave sterilizer

This study evaluates the performance of a continuous microwave device in the sterilization of oil palm fruits spikelet. The device comprises four microwave generators (magnetron), a tunnel cavity driven by a belt conveyor, and a tray as a container for palm fruit. This study aims to evaluate the distribution and penetration of microwave energy into palm fruit and to examine the quality of palm oil concerning power density and residence time adjusted in this study. Continuous microwave sterilizer was operated at various masses of oil palm fruit (0.5, 1, 1.5 kg), residence time (6, 8, 10, 12, 14 min), and microwave power (180, 300, 450, 600, 800 W). The resulting temperature in this study ranged from 39 to 97 °C. Observation of the temperature gradient inside-out of a single fruit indicates the interior temperature at the kernel nut is always higher as compared to exterior temperature (abscission layer), with temperature differences ranging from 3 to 23 °C. A minimum power density of 300 W/kg, a residence time of 6 min, and a temperature of 50 °C were required to produce palm oil with FFA less than 5%. Performance indicators of the prototype used in this study are a number of moisture loss dan oil quality. The moisture loss during the sterilization process was around 0.5 to 10.6% which indicates some water content in the fruit, while the content of water, FFA, β-carotene and vitamin E ranging between 1.9 and 17.6%, 0.32-1.74%, 186.14-608.59 ppm and 165.47-610.17 ppm, respectively. © 2001 Elsevier Science. All rights reserved.

Measurement of reaction temperature distribution inside of methanol steam reforming microreactor using infrared thermography

Methanol steam reforming is a promising method for in-situ hydrogen production and greatly affected by the reaction temperature inside the microreactor, while the inside reaction temperature distribution is quite difficult to be measured. Here, we developed a visible methanol steam reforming microreactor using optical crystal as observation window and using infrared thermography to measure the real-time reaction temperatures. The method of using infrared thermography to measure the distribution of reaction temperature was presented and characterized with the accuracy of 98.4 % in the range of 300.0–575.0 K. Then, temperature heating and hydrogen production tests were conducted, and results showed that the lower oxygen to carbon (O/C) ratio leads to higher heating rate of 18.0 K/min during microreactor heating stage. The measured temperature distribution on the copper foam increases with a stable gradient of 0.91 K/mm along the reactant flow direction and the temperature difference in vertical direction is less than 10.0 K. The maximum methanol conversion is 98.0 % at the gas hourly space velocity (GHSV) of 3600 mL/(g·h) and maximum reformate flow rate is 100.8 mL/min at the GHSV of 6000 mL/(g·h). The obtained results demonstrated that the visible methanol steam reforming microreactor and reaction temperature measurement method would be beneficial for future microreactor’s design.

Numerical computation on cavity natural convection for built-in plate arrays application: Heat transfer analysis and optimization

Natural convection in cavity with built-in plates has been widely used in fluid mechanics and heat transfer engineering, such as heat exchangers, electronics, solar collector, growing crystals, etc. However, the natural convection flow physics and heat transfer characteristics in cavity with plate arrays remain to be investigated further. In this study, numerical analysis and computational fluid dynamics simulation are conducted for natural convection in cavity with plate arrays by finite volume method. Key influence factors impacting heat transfer are analyzed, including the line dip-angle of plate arrays θ, rotary angle of plates to the array φ, with relationships comparison between the Nusselt number and Rayleigh number in different built-in plate arrays. Moreover, for illustrative application example, the natural convection in solar greenhouse with PV arrays roof is investigated, with inside temperature distribution comparison under different design parameters. The preliminary results indicate that plates spacing could remarkably impacts the number of streamlines between ”late’arrays. The dip-angle of arrays θ leads to different shape flow in the cavity, and the rotary angle of plates φ notably affects the fluid flow direction in the vicinity areas of plates, especially when φ = 90°. Solar greenhouse case study indicates that increasing array group numbers can improve air temperature distribution uniformity in the cavity, which is favorable for built environment accurate control and operation. This work can provide modeling method support and reference for natural heat convection applications.

PCMs’ performance and the benefit enhancement

At present, non-renewable energy sources such as oil are being consumed in large quantities and, along with this energy consumption, large quantities of carbon dioxide (greenhouse gases) are being produced, contributing to increased global warming. The energy used to control the interior temperature of a building area cannot be disregarded since the building industry, as a significant energy consumer and CO2 emitter, has a significant influence on the reduction of greenhouse gas emissions. Due to their enormous thermal energy storage capacity, phase change materials may be employed in building envelopes, where they can help conserve energy and somewhat lower carbon emissions. In this paper, the thermal performance of phase change materials that can be applied to the building sector is summarised and compared, while various ways of improving the ratio of thermal efficiency to cost are proposed based on their practical use, from material enhancement, production method enhancement, and the choice of use and location for efficiency enhancement.