Increasing Heat Load Research Articles

Inferring the scrape-off layer heat flux width in a divertor with a low degree of axisymmetry

Plasma facing components (PFCs) in the next generation of tokamak devices will operate in challenging environments, with heat loads predicted to exceed 10 MWm−2. The magnitude of these heat loads is set by the width of the channel, the ‘scrape-off layer’ (SOL), into which heat is exhausted, and can be characterised by an e-folding length scale for the decay of heat flux across the channel. It is expected this channel will narrow as tokamaks move towards reactor relevant conditions. Understanding the processes involved in setting the SOL heat flux width is imperative to be able to predict the heat loads PFCs must handle in future devices. Measurements of the SOL width are performed on the high-field spherical tokamak, ST40, using a newly commissioned infrared thermography system. With its high on-axis toroidal magnetic field (≥1.5 T) ST40 is uniquely positioned to investigate the influence of toroidal field on the heat flux width in spherical tokamaks, whilst also extending measurements of the SOL width in spherical tokamaks to increased poloidal field (≥0.3 T). Due to the divertor on ST40 having a low degree of axisymmetry, it is necessary for a set of radial measurements of the heat flux to be taken across the divertor, made possible using an automated toolchain that fully incorporates its 3D geometry. These radial profiles are combined with the magnetic geometry of the plasma to infer the width of the SOL, with both Eich and double exponential profiles of heat flux observed. A reduction in the heat flux is observed toroidally across part of the divertor, along with increased heat loads observed locally around the edges of the tiles. Future work in characterising the impact of tile misalignment and uncertainties in the reconstructed divertor magnetic geometry is required in order to further understand the observed heat flux patterns, as are additional investigations into the role potentially being played by an inhomogeneous sheath electric field.

Assessing awareness of IoT-driven strategies for poultry management in mitigating increased ambient heat in Enugu, Nigeria

The study examined awareness level of Internet of Things (IoT)-driven strategies in mitigating impacts of increased ambient heat load in poultry pens by poultry farmers in a smart city like Enugu, Nigeria. With the rising challenges of climate change, increased ambient heat load within poultry pens poses a significant threat to poultry production. Understanding farmers’ perception of impact of increased ambient heat load and their awareness of IoT-driven strategies for its mitigation is crucial for sustainable poultry system management in smart cities. Multi-stage random sampling technique was used to select 240 poultry farmers from the three Local Government Areas that make up Enugu City. A structured questionnaire was used to collect data from the respondents. Descriptive statistics and Likert rating scale were used to analyze the data. The study identified socio-demographic factors influencing farmers’ perception of impact of increased heat load and awareness/ adoption of IoT-driven mitigation strategies. Education level (45% secondary education), access to information (29.2%) and financial resources (22.9%) were key determinants. The findings revealed varying levels of awareness among poultry farmers regarding IoT-driven strategies while the constraints faced by farmers in implementing sustainable IoT-driven mitigation strategies included lack of awareness, lack of funding/high initial investment, limited access to technology, inadequate training, poor extension contact, water availability and climate variability. The study concluded that majority of poultry farmers shared similar perceptions about the impact of increased ambient heat load on poultry species but however were not aware of many of the IoT-driven strategies to mitigate the impact and were limited by a number of constraints or challenges to adopting IoT-driven mitigation strategies which altogether could improve poultry production system and help to achieve animal protein security in a smart city like Enugu, Nigeria. The study further recommended enlightenment of poultry farmers on the impact of increased ambient heat load on poultry species and available/sustainable/harmonized IoT-enabled guidelines or solutions to mitigate heat load in smart cities’ poultry production system.

Povezanost med vročinskimi valovi in obiski na Internistični prvi pomoči Univerzitetnega kliničnega centra Ljubljana v obdobju 2013–2017

Background: Heatwaves have a severe impact on the number of deaths and emergency department visits, making them the most hazardous natural disaster due to climate change in many regions of the world. Our aim was to assess the short-term association between emergency department visits and heat waves from 2013 to 2017 to see whether any difference in the number of visits occurred at the Emergency Department in Ljubljana University Medical Centre during that period. Methods: The design of our study is a retrospective cross-sectional epidemiologic study. We estimated relative risks (RR) for a number of ED visits during heatwave days and reference period days for the observed diagnoses (all causes, diseases of the circulatory system, respiratory system, endocrine diseases, diseases of the digestive system and genitourinary diseases) sex, and age (from 19 to 74 years old, 75 years old and older), as well as 99.6% confidence intervals (CI) and excess ED visits in percent (%) associated with heatwaves occurring in the years from 2014 to 2017. Data were analyzed for the patients arriving at the Emergency Department of the Ljubljana University Medical Centre during summer time, from May to September. The region covers around 550,000 people and is considered an urban and rural area. Results: The results of our study showed that there was no statistically significant increase in number of ED visits during heatwaves for all causes in all observed years. We noticed even statistically significant protective phenomena between heatwaves and the number of ED visits. These happened in the years 2015 and 2017 for both sexes and circulatory system diseases, in 2016 for men, circulatory system diseases, and in 2015 for respiratory system diseases. We showed a statistically significant association between heatwaves and the number of visits in the ED for endocrine diseases in 2013. Conclusion: Despite the increased heat load in the last observed years, the number of ED visits in Ljubljana has remained stable or even decreased. Further studies on how each intervention affects the behavior of the observed population are needed to clarify whether public health measures and inter-sectoral cooperation impact the number of ED visits.

Experimental and numerical investigation of the effects of passive radiative cooling-based cool roof on building energy consumption

Passive radiative cooling is an energy-efficient method that reduces indoor temperature and cooling load in buildings, thus contributing to significant energy savings. This study investigates the thermal performance of the passive radiative cooling-based cool roof (PRC-CR) based on experimental and numerical analysis in terms of indoor air temperature and space cooling load indicators. Two experiment rooms constructed from concrete are developed with an indoor air temperature control system. One is the PRC-CR room with the roof covered by a passive radiative cooling metamaterial and the other is the reference room with a concrete roof. Long-term testing results in Hefei show that the indoor air temperature of the PRC-CR room is 5.5 °C lower in maximal and 1.8 °C lower on average than that of the reference room in summer when the indoor air temperature control system is off. Besides, when the indoor air temperature control system is switched on, the PRC-CR room achieves a 29.1% reduction in daily cooling load in summer and a 4.1% increase in daily heating load in winter, which suggests that passive radiative cooling can indeed save energy in cooling season (i.e., hot season) but cause overcooling in heating season (i.e., cold season). In addition, a simulation building model is developed to further investigate the effect of the PRC-CR on the energy consumption of buildings in different locations. The predicted results show that PRC-CR reduces the total load of buildings in cooling load prevailing regions (e.g., tropical zones, subtropical zones, and the vast majority of warm temperate zones), while increasing the total load of buildings in heating load dominant regions (e.g., most middle temperate zones, cold temperate zones, and plateau climate zones). In summary, this work demonstrates both the positive and negative effects of PRC-CR, providing valuable insights into PRC-CR applications.

Heat transfer characteristic of an alumina oscillating heat pipe

Oscillating heat pipes (OHP) are a promising and highly efficient heat transfer technology especially in the field of power electronics thermal management. However, conventional metal OHP do not meet the need for insulation or low coefficients of thermal expansion. In order to expand the application field and break the application limitation of the OHP technology, alumina ceramic oscillating heat pipes was designed and investigated in this paper. The alumina OHPs combine the excellent insulating, oxidation-resistant, corrosion-resistant and low thermal expansion properties of alumina ceramic with the efficient heat exchange mechanism of oscillating heat pipe technology, exhibiting great application potential. An alumina flat-plate oscillating heat pipe was prepared, 6 internal microchannels were examined using micro-CT, and the microstructure was characterized using scanning electron microscopy. The heat transfer characteristics of the OHP charged with water were investigated using a heat transfer test system. Increasing heat loads were employed to the OHP, and the operating temperature of 20 °C and 60 °C as well as the orientation varied between 0° and 90° were also introduced. The oscillation motion of the alumina OHPs were investigated, including temperature oscillations before and after startup of the OHPs, and a comparison effective thermal conductivities at various tilt angles and operating temperatures was carried out. The experimental results revealed that the heat transfer performance of the alumina oscillating heat pipe significantly increased with the increased heat loads and reached to 861.7 W/(m∙K) at 56 W. The effective thermal conductivity of the OHP was 6 times higher than that of the empty OHP at heat load of 16 W. When the orientation was 30°, the temperature oscillation instability increased, the oscillation amplitude increased, and the heat transfer performance of the oscillating heat pipe decreased. As the operating temperature increased, the stability of temperature oscillations improved, the amplitude decreased, and heat transfer performance was enhanced.

Design of the Cooling Water System Upgrade for 42 T Resistive Magnet at the CHMFL

Abstract To meet the operation requirements of the 42 T resistive magnet which will be built by the Chinese High Magnetic Field Laboratory (CHMFL) in the future, the cooling water system needs to be upgraded accordingly. The cooling water system will improve its performance based on the existing cooling system. This article will make a detailed analysis of the system upgrading and transformation plan. In terms of refrigeration, to meet the requirements of larger refrigeration temperature difference, a new centrifugal chiller with large temperature difference will be added in series with the existing unit of refrigeration. With the increase in heat load, the system will connect a new plate heat exchanger in parallel on the basis of the original heat exchange capacity. However, the circulating cooling water flowrate of the 42 T resistive magnet is expected to exceed 1200 m3/h, the purification flowrate of the deionized water also needs to be upgraded, and the purification ratio is expected to reach more than 6%. In addition, the control system will be also combined with the new equipment and pipelines to realize a variety of chilled water storage and supply modes to better meet the operation of the new-built magnet.

Study on the Operation Optimization of Medium-Depth U-Type Ground Source Heat Pump Systems

Deep geothermal energy is a sustainable and renewable spacing heating source. Although many studies have discussed the design optimization of deep borehole systems, few have accomplished optimization and in-depth analysis of system operation control. In this study, an analytical model of the U-type deep borehole heat exchanger is proposed, and the average relative error between the simulated outlet temperatures and experimental data is −3.2%. Then, this paper presents an integrated model for the operation optimization study of the U-type deep-borehole ground source heat pump system. The optimal control of flow rate is adopted to match the variation in heating load. Compared with the constant-flow rate (110 m3/h) operation mode, the variable flow rate method reduces the power consumption of the heat pump and circulating pump by 22.1%, from 288,423 kW·h to 224,592 kW·h, during 2112 h of operation. In addition, the system has a larger RHS and COP when the thermal conductivity of the backfill material increases. When the borehole depth increases by 200 m from 2300 m, the energy consumption of the circulating pump will drop from 85,844 kW·h to 56,548 kW·h. The COP of the heat pump unit will decrease approximately linearly as the heating load increases, and the total power consumption will increase accordingly. This work can provide guidance for the design and optimization of U-shaped GSHP systems.

Investigating the transient conditions of “Sabat” space and its influence on pedestrian sensations during thermal walks. Algiers’ Casbah case study

Cities are already witnessing the impacts of climate change. Prolonged heat exposure have a direct effect on pedestrians’ thermoregulatory system, causing serious heat-related issues in the form of fatigue and thermal exhaustion. While the human body is capable of maintaining heat balance, excessive heat exposure combined with increasing heat loads can deteriorate the thermoregulatory process which leads to discomfort. Walkability is one of the significant challenges for climate change mitigation. Balancing the dichotomy of walking to mitigate climate change, and mitigating climate change to walk emphasizes the importance of promoting resilient walkability. In this context, the term “resilience” is used to highlight the need to design urban spaces able to adapt to increased urban heat, enabling pedestrians to tolerate and recover from discomfort conditions. This study investigates the potential of the “Sabat”, a traditional semi-outdoor space with lift-up design, and its distribution in generating transient thermal aeraulic conditions, and reducing fatigue sensation, hence, supporting a positive walking experience. Thermal walks have been conducted in Casbah of Algiers during temperate and hot weather conditions, in the context of uphill walking. Results revealed the alliesthesial effect of cool-shaded and ventilated Sabats to reduce fatigue sensation, which was confirmed by the significant correlation at lag-(-1) (r = 0.504, p < 0.001). Findings shed light on the importance of maintaining dynamic alliesthesia to create modulated restorative opportunities and offer starting point for hypothesizing broader trends for future implementation of Sabat design in modern cities.

Experimental study on the thermal performance of aluminum three-dimensional vapor chamber heat sink with a louvered-fin stacked evaporator wick for data center servers

Under increasing heat loads and stricter energy consumption limits for data center servers, traditional heat sinks are becoming inadequate. In this paper, a novel aluminum three-dimensional vapor chamber heat sink of air cooling is developed, in which the evaporator and condenser are connected internally to form a three-dimensional flow channel for working fluid so that two heat transfer methods, phase change and single-phase, are combined in one device. Furthermore, a novel louvered-fin stacked evaporator wick structure and its fabrication process are proposed, which greatly improve thermal performance and temperature uniformity. Thermal characteristics under different heat loads, fan input power, and tilt angles are studied experimentally. Results show that the heat sink has a maximum heat dissipation capability of more than 450W, at which the maximum evaporator surface temperature is within 75 °C. The fan input power can distinctly improve thermal performance, heat load impacts overall thermal resistance slightly and the minimum is 0.083 °C/W. The tilt angle impacts thermal resistance slightly but significantly affects both the evaporator surface and condenser fin temperature uniformity. Under a tilt angle of 90°, regardless of heat loads, the condenser fin temperature is much lower than other tilt angles.

Single-phase thermosyphon heat transport device, a future prospect for heat removal applications: An experimental comparison with heat pipe and two-phase closed thermosyphon

Over the years, the passive mode of heat transportation has gained immense popularity, which includes two-phase devices viz. Heat pipe (HP) and Two-phase closed thermosyphon (TPCT). But recently, the thermosyphon heat transport device (THTD) entered the pool, wherein the heat transfer fluid (HTF) in liquid phase transports heat by natural circulation (thermosyphon). Hence, to gauge their efficacy, in the present experimental investigation, the three devices (with the same geometry and HTF) are compared by imposing isothermal (40°C–90 °C) and isoflux (50–900 W) heating conditions.In isothermal mode, HP transports heat with a minimal temperature gradient compared to TPCT and THTD. The thermal resistance (TR) of TPCT and THTD is 5.4 to 10.1 times and 6.6 to 10.1 times respectively greater than HP. For isothermal temperatures below 80 °C, the TR of THTD is less than TPCT (viscous limit). Later the trend reverses as the TPCT outperforms, while THTD experiences HTF boiling. Further, the heat extracted by HP is 2.1 to 3.9 times and 3 to 3.5 times greater than TPCT and THTD respectively. Hence, its application is justified if cost is not a concern, while THTD (with high-temperature HTF) is suggested over TPCT on an economic basis. Even the isoflux mode showed a similar trend of TR. The system response (based on time constant) depicted both HP and TPCT have similar and nearly constant values over the heat load range, while in THTD, it decreases with an increase in heat load and approaches the other two. Hence, a high-temperature HTF would lead to competitive results. Further, concerning the heat transport distance, as the TR of THTD remained the same compared to the increment in TPCT, the application of the former is justified in long-distance heat transportation. Ultimately, HP is the front-runner, while TPCT and THTD perform on par depending on operating conditions and geometry.

Thermal performance and stability experiments of a 1.75-meter-long helium pulsating heat pipe

Experimental studies of the performance and thermal stability of extended-length helium pulsating heat pipes (PHPs) were performed at the University of Wisconsin – Madison. Multiple distinct testing procedures were carried out on helium PHPs with an adiabatic length of 1.75 meters, such as progressively increasing evaporator heat load, randomized heat load, and extended period tests. The results of these tests show that despite the stochastic nature of the fluid flow and persisting non-equilibrium conditions, long-distance helium PHPs can maintain stable and steady operation with excellent thermal performance. The progressively increasing heat load tests serve as a baseline for the 1.75-meter PHP’s performance, where the maximum effective conductivity observed was 443.4 kW/m-K at 570 mW heat load and a fill ratio of 56.42%. Furthermore, the randomized heat load test show that, with an optimized fill ratio, PHP performance is not strongly dependent on previous operating conditions and that normal operation can be swiftly recovered from a dry-out condition. The extended period test shows a stable, pseudo-steady operation for over 50 hours with no performance degradation or temperature deviations observed. The impact of PHP build quality is also discussed.

Integrating project management with advanced cooling solutions for data centers: A path to enhanced energy efficiency

Data centers play a crucial role in modern digital infrastructure, but their energy consumption and associated carbon footprint are significant concerns. Among the various energy-consuming components of data centers, cooling systems stand out as major contributors. This paper explores the integration of project management principles with advanced cooling solutions to enhance energy efficiency in data centers. By effectively managing projects and implementing innovative cooling technologies, data center operators can achieve significant reductions in energy consumption and operational costs. The integration of project management practices with advanced cooling solutions involves several key steps. First, project management methodologies such as Agile or Waterfall are applied to plan and execute the implementation of advanced cooling technologies. This includes assessing current cooling systems, identifying suitable advanced solutions, and developing a timeline for implementation. Next, advanced cooling solutions such as liquid cooling, containment systems, or free cooling are deployed to reduce the energy required for cooling data center equipment. One of the primary benefits of integrating project management with advanced cooling solutions is enhanced energy efficiency. Advanced cooling technologies can significantly reduce the energy consumed by data center cooling systems, leading to lower operational costs and a smaller carbon footprint. Additionally, the use of project management methodologies ensures that the implementation of these technologies is carried out efficiently and effectively. Furthermore, this integration can lead to improved data center performance and reliability. By optimizing cooling systems, data center operators can ensure that IT equipment operates within optimal temperature ranges, reducing the risk of overheating and downtime. Additionally, the implementation of advanced cooling solutions can future-proof data centers against increasing heat loads from high-density computing equipment. In conclusion, integrating project management with advanced cooling solutions offers a promising path to enhance energy efficiency in data centers. By adopting this approach, data center operators can achieve significant energy savings, reduce their environmental impact, and improve overall operational efficiency.

Investigation on the Influence of the Condenser Length and Its Coupling Effect With Elevation on the Performance of Loop Heat Pipe

Abstract The effects of condenser length and evaporator/condenser elevation on the performance of a loop heat pipe (LHP) in a gravity field were investigated, respectively, as well as their coupling effect. The refrigerant R40 was selected, and the condenser length was altered by changing the number of fins connected to the water-cooled plates. The experiments were conducted at three evaporator/condenser elevations: zero elevation, favorable elevation, and adverse elevation. The experimental results indicated that the evaporator temperatures of LHP with three different condenser lengths are very close when the LHP operates in variable conductance mode (VCM). However, an excessively long condenser will increase the LHP thermal resistance in VCM. In constant conductance mode (CCM), the longer the condenser, the lower the evaporator temperature. As the heat load increases, the LHP first exhibits gravity-driven mode and then capillarity-gravity-driven mode at a favorable elevation. The positive coupling effect on reducing the evaporator temperature by extending the condenser length and running at a favorable elevation manifests that the influence of condenser length is very small in gravity-driven mode, while in capillarity-gravity-driven mode, the effect of operating at a favorable elevation gets weakened, and the positive effects of the two factors cannot be simply calculated by the linear superposition principle. Additionally, reverse flow and flash evaporation were also observed and analyzed in depth. These results and conclusions can be used to guide the design of the condenser and the installation of LHP for ground applications.

Energy consumption and thermal comfort assessment using CFD in a naturally ventilated indoor environment under different ventilations

The rising energy demands of modern buildings necessitate the proper balance between occupant comfort and energy efficiency. This study numerically evaluates the effect of different inlet and exhaust vent profiles on indoor IEQ and energy consumption in well-validated, occupied office buildings for a cold climate conditions. Using ANSYS products, the research evaluates the impact of different ventilation configurations on occupant comfort using different comfort parameters such as, PMV, PPD, air temperature, temperature gradient, fluid flow velocity. The study also analyze how different ventilation configurations affect the thermal load on the radiator for indoor thermal comfort. The findings reveal a significant effect of ventilation profiles on both IEQ and energy consumption. Inadequate ventilation configuration selection can lead to a significant increase in radiator heat load, potentially increase up to 117.3%. Conversely, the adoption of an optimized ventilation strategy can simultaneously reduce energy consumption and improve indoor occupant thermal comfort. Indoor occupant comfort with minimal radiator heat load can be achieved using vertically oriented, rectangular inlet and exhaust vents with a perimeter ratio of 0.611. This research contributes to the development of sustainable buildings and describes indoor comfort design for cold climate conditions.

Investigation of operational limit of a pulsating heat pipe by estimating local heat transfer

How pulsating heat pipes (PHPs) reach their operational limit has not yet been fully understood. This study aims to provide a complete picture of the termination mechanism of the self-oscillation of vapor and liquid. Experimental studies on a 10-turn PHP with HFC-134a were conducted and the filling ratio (FR) was from 20% to 80%. The thermo-fluid behavior in the PHP was investigated by temperature measurements with a high-resolution and high-speed infrared camera and estimation of fluid-to-wall heat flux distributions by solving inverse heat conduction problems. The results suggested that the PHP, increasing heat load, reached the operational limit due to different mechanisms depending on the filling ratio: at a high FR (80%), the liquid volume ratio increased with the increase of the operating temperature, resulting in the compressed liquid phase. At a low FR (20%), when a large amount of heat was applied, the fluid in the evaporator dried out and became a superheated vapor. The PHP with an optimum FR (50%) transferred the maximum heat under the same evaporator temperature, as the fluid in the PHP was able to keep the saturated two-phase state until the evaporator temperature exceeded the critical temperature.

Experimental investigation on a flat loop heat pipe coupled with thermoelectric cooler

The flat Loop Heat Pipe (LHP) has the advantages of small size, light weight, and direct contact with the heat source without additional thermal resistance, which has gradually drawn attention and importance in the aerospace field. However, for the vertically arranged flat LHP, there is a significant amount of reverse heat leakage from the evaporator to the compensation chamber, resulting in a low operating efficiency of the heat pipe. This paper proposes a thermal control structure coupling the flat LHP with thermoelectric cooler (TEC), which investigates the effects of TEC on the start-up speed, working temperature, system thermal resistance, temperature fluctuation, and reverse temperature control of the flat LHP through experimental studies. The results show that the TEC can help improve the start-up speed of the heat pipe by approximately 50 % under low heat load. The heat resistance of the LHP is greatly reduced to approximately 0.13–0.15 °C/W, and the working temperature curve changes from “V” type to a linear line with increasing heat load power. Moreover, by using the TEC to provide reverse power to the compensation chamber for temperature control, the temperature control efficiency is extremely high, and a temperature rise of approximately 10 °C can be achieved with only 0.1 W TEC power. The above research indicates that the TEC can significantly weaken the disadvantage of the flat LHP and improve its engineering practicality.

Study on the Influence of Fan and Fan Cowl on Intake Air Parameters of Cooling Module

Abstract Due to the increase in heat load, the demand for heat dissipation of the cabin cooling module has increased. The fan arrangement and the design of the fan cowl can significantly affect the intake air parameters, thereby affecting the performance of the heat exchangers. In this paper, the whole vehicle model was set up and the effect of the fan installation distance, the fan cowl coverage ratio, and the radial extension of the fan cowl outlet was researched by numerical simulation. The results show that due to the relative position of the layout of the cooling module, the effect of the fan arrangement and the fan cowl design on the intake parameters of the radiator is greater than that of the intercooler. The improvement of the air velocity uniformity can reduce the intake air average temperature for better heat dissipation, a 2% improvement in air intake velocity uniformity can lead to a 6% reduction in air intake average temperature event at a low air mass flow. The greater installation distance of the fan or the higher closing degree of the fan cowl, the more favorable intake parameters to ensure the better cooling performance of the heat exchangers. Moreover, when the fan cowl coverage ratio reaches 0.9, the air intake average temperature increases by 5.6%, which means that the fan cowl coverage should not be too high. This study will provide useful reference information for the design of cooling modules in the cabin.

EXPERIMENTAL STUDY ON TWO-PHASE NONLINEAR OSCILLATION BEHAVIOR OF MINIATURIZED GRAVITATIONAL HEAT PIPE

An experimental study on oscillation behavior of vapor-liquid two-phase flow in an ethanol-filled aluminum miniaturized gravitational heat pipe with parallel rectangular channels is carried out. The nonlinear oscillation behavior and oscillation characteristics of two-phase flow in the oscillation state are qualitatively analyzed. In addition, the nonlinear oscillation characteristic of the wall temperature is revealed. Furthermore, the influence of heat load on temperature oscillation characteristics is further analyzed. The research shows that the independent oscillation in a single channel characterized by the random formation and oscillation of liquid plug in a single channel is the typical oscillation behavior of two-phase flow under medium heat load (&lt;i&gt;Q&lt;/i&gt; &amp;#61; 28 W). In addition, the interaction on oscillation of liquid plugs between adjacent channels is small. For high heat load (&lt;i&gt;Q&lt;/i&gt; &amp;#61; 45 W), the vapor pressure difference at both ends of the liquid plug has a more important role in promoting the liquid plug, the superposition of the liquid plug oscillation in single channel and the oscillation between adjacent channels forms the interference oscillation in adjacent channels. For interference oscillation in adjacent channels, under coupling erosion of the liquid plug in a single channel and the liquid plugs in adjacent channels, with increase of heat load (&lt;i&gt;Q&lt;/i&gt; increases from 38 W to 45 W), the dominant frequency of oscillation for independent oscillation in a single channel increases (from 2.5 Hz to 4.2 Hz), and the larger driving force caused by heat load increase enhances the oscillation of liquid plug in a single channel and weakens the oscillation of liquid plug in different channels for interference oscillation in adjacent channels.

Comparison of models for the relationship between respiration rate or rectal temperature and increased heat load in farm animals

Heat stress is an increasing challenge for production animals, particularly in warmer regions of the world. The aim of this study was to compare the fit of three different relationships when modelling respiration rate (RR) and rectal temperature (RT) in animals exposed to increased load.Data from three published studies on finishing pigs, gestating sows and dairy cows were analysed. RR and RT are characterized by being unaffected by increased heat load as long as it is kept below a certain level, and in warmer conditions they increase with increased heat load. As an expression of heat load either the air temperature or the ET (Effective Temperature) was used. The ET unites the effect of air temperature, air humidity and velocity on the animal perception of increased heat load. The relationship between RR and RT and the temperature or the ET was analysed by multiple change point regression and the cubic relationships were modelled. In general, the models provided better fits for RR compared to RT.Relationships with an unaffected piece followed by a quadratic relationship and the cubic relationships performed nearly equally well. Using ET resulted in better correlations than using temperature alone for gestating sows and dairy cows.

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.