Total Heat Load Research Articles

Seasonal and between-population variation in heat tolerance and cooling efficiency in a Mediterranean songbird

Discrete populations of widely distributed species may inhabit areas with marked differences in climatic conditions across geographic and seasonal scales, which could result in intraspecific variation in thermal physiology reflecting genetic adaptation, phenotypic plasticity, or both. However, few studies have evaluated inter-population variation in physiological responses to heat. We evaluated within- and inter-population seasonal variation in heat tolerance, cooling efficiency and other key thermoregulatory traits in two Mediterranean populations of Great tit Parus major experiencing contrasting thermal environments: a lowland population subject to hotter summers and a higher annual thermal amplitude than a montane population. Specifically, we measured heat tolerance limits (HTL), body temperature, resting metabolic rate, evaporative water loss, and evaporative cooling efficiency (the ratio between evaporative heat loss to metabolic heat production) within and above the thermoneutral zone during winter and summer. Heat tolerance during summer was greater in lowland than in montane birds; indeed, lowland birds seasonally increased this trait to a significant level, while montane ones did to a lesser extent. Besides, lowland birds showed greater evaporative cooling efficiency during summer (possibly due in part to reductions in total endogenous heat load), while surprisingly montane ones showed the opposite trend. Thus, lowland birds displayed greater seasonal flexibility in HTL, body temperature and resting metabolic rate above thermoneutrality, thus giving some support to the climatic variability hypothesis — that flexibility in thermoregulatory traits should increase with climatic variability. Our results partially support the idea that songbirds’ adaptive thermoregulation in the heat is flexible, highlighting the importance of considering intraspecific variation in thermoregulatory traits when modelling the future distribution and persistence of species under different climate change scenarios.

Investigation of pedestal parameters and divertor heat fluxes in small ELM regimes in DIII-D

Abstract Divertor heat flux and its correlation with pedestal parameters within various small edge localized mode (ELM) regimes, including high beta poloidal, type-II and ELMs with negative triangularity H-modes were investigated in DIII-D. The parallel energy fluences of type-II and high beta poloidal small ELM regimes fall below the linear scaling with pedestal electron pressure for type-I ELMs put forward in Eich et al 2017 (Nucl. Mater. Energy 12 84–90). The negative triangularity of H-mode ELMs follow the Eich scaling for type-I ELMs. The parallel heat flux and total heat loads to the divertor were determined using high-time resolution infrared thermography, while pedestal parameters were obtained through self-consistent kinetic equilibrium reconstructions. Linear regressions for the type-II and high beta poloidal regimes demonstrate that an equivalent 7.5 MA small ELM scenario in ITER would fall below the ~5 MJ m − 2 leading edge melting limit for tungsten (Gunn et al 2017 Nucl. Fusion 57 046025). Utilizing fast thermography, the scrape-off layer power fall-off length for both inter-ELM and intra-ELM was determined and compared to the Eich scaling with poloidal magnetic field in Eich et al (ASDEX Upgrade Team and JET EFDA Contributors 2013 Nucl. Fusion 53 093031). Except for the high beta poloidal scenario, all the small ELM regimes during both inter- and intra-ELM periods had power fall-off lengths ( λ q ) larger then would be expected from the B pol , MP − 1 scaling associated with type-I ELMs, signifying their potential in managing heat loads and offering a solution for core–edge integration.

Performance investigation of a solar-driven cascaded phase change heat storage cross-seasonal heating system for plateau applications

The mismatch between solar radiation resources and building heating demand on a seasonal scale makes cross-seasonal heat storage a crucial technology, especially for plateau areas. Utilizing phase change materials with high energy density and stable heat output effectively improves energy storage efficiency. This study integrates cascaded phase change with a cross-seasonal heat storage system aimed at achieving low-carbon heating. The simulation analyzes heat distribution and temperature changes from the heat storage system to the heating terminal. The results indicate that although the solar collectors operate for 26.3% of the total heat storage and heating period, the cumulative heat stored is 45.4% higher than the total heating load. Heat transferred by the cross-seasonal heat storage system accounts for up to 61.2% of the total heating load. Therefore, the system reduces fuel consumption by 77.6% compared to conventional fossil fuel heating systems. Moreover, radiant floor heating terminals, with a wide range of operating temperatures, match well with cascaded phase change heat storage and can reduce operation time by 19.5% and heat demand by 5.2% compared to conventional radiators. In addition to demonstrating the feasibility of applying cascaded phase change technology in cross-seasonal heat storage heating, this study reveals the lifecycle sustainability due to the shortened heat storage period. The configuration, parameters, and simulation results provide a reference basis for system application and design.

Prediction of airflow temperature in coal mining face under the influence of multiple heat sources coupling: Numerical simulation and verification

With the development of coal resources to the deep, the mine heat damage has become increasingly serious. In this work, we proposed a comprehensive airflow temperature prediction model considering the coupling effect of multiple heat sources in coal mining face. The model was then discretized and a coupled solution simulator was developed independently. Finally, we conducted field test to verify the simulation results, and carried out a multi-factor sensitivity analysis affecting the thermal environment of coal mining face. The results show that:(i) The maximum relative error of prediction results is less than 4 %, which verifies the reliability of the prediction model. (ii) Heat dissipation from electrical equipment, surrounding rock and hot airflow leakage of gob area account for 43.8 %, 28.8 % and 17.4 % of the total heat load, which are the main causes of heat damage. (iii) The maximum airflow temperature in coal mining face increases in a parabolic trend with average advance speed. (iv) As the original rock temperature increases, the thermal environment of coal mining face deteriorates rapidly. (v) Cooling the inlet airflow or increasing the airflow volume can alleviate the high temperature problem. This research can provide guidance for the treatment of deep mine heat damage.

Impact of tent shade on heat exposures and simulated heat strain for people experiencing homelessness.

Concurrent increases in homelessness and heat intensity, duration, and frequency translate to an urban heat risk trap for the unsheltered population. Homelessness is both a driver and consequence of poor health, co-creating distinct geographies with various risk factors that exacerbate heat vulnerability. We tested the efficacy of different tent shadings over identical tents often observed in the Phoenix area (white bedsheet, mylar, tarp, and aluminum foil) and compared them to a control tent (uncovered) and ambient conditions. We monitored all meteorological variables at all six locations, notably Mean Radiant Temperature (MRT). The in-tent microclimate variability was applied to complete statistical and physiological modeling including substance use on heat strain. Findings indicate that tent shadings resulted in significantly lower in-tent MRT during the day (p < 0.05), but exacerbated in-tent thermal risk during the night compared to the control tent and ambient conditions. Furthermore, we found evidence that the temperature metric matters, and using only either MRT or air temperature (Tair) to assess "heat" could lead to inconsistent conclusions about in-tent microclimate. Interactions between shade types and time significantly amplified in-tent thermal risk. Physiological modeling indicates a higher risk of heat strain (core temperature beyond 40˚C) for people using substances. Decision makers should promote testing different heat intervening strategies toward realizing effective means of protecting human life and preventing heat illnesses. This study illuminates the need for an interdisciplinary approach to studying tents as shelters that considers the total heat load with heat strain modeling.

Thermal performance research on the zero liquid helium consumption cryostat for a superconducting undulator

Superconducting undulators generally depend on a liquid helium cryostat. If the cryostat can liquefy the boil-off helium completely, a large helium refrigerator can be avoided, and a large amount of electrical energy can be saved. However, many studies are limited by the excessively high heat load. In this work, systematic thermal analysis and optimization are carried out to minimize the total heat load so that it can be covered by the cooling capacity. Based on the analysis, one single thermal shield is set in the cryostat, and thermal interruptions are widely adopted together. Moreover, the cooling capacity matches the heat load well, and the excess cooling capacity is increased significantly. In the experiment, the cryostat was tested with no magnet, a small magnet and a full-scale magnet respectively so that the heat load could be analyzed step by step. Finally, zero liquid helium consumption was achieved with the full-scale superconducting magnet, which reached a current of 450 A. The excess cooling capacity accounts for approximately 40 % of the total cooling capacity, which is as high as approximately 2.0 W. This study can serve as a reference for the research of superconducting undulator and other magnet cryostats.

Reservation of the heat supply system with biofuel heat energy sources

The implementation of the reservation of the heat supply system to a populated area was analyzed. It is noted that increasing the reliability of heat supply to consumers is a fundamental task, especially given the current military situation in Ukraine. The solution to this difficulty is considered when reserving heat supply by constructing a backup source of thermal energy using alternative types of fuel. A combined thermal scheme for connecting a hot water heat generator using biofuel to the existing city heat supply system is proposed to increase its reliability and survivability, which ensures the efficiency and reliability of operation of the heat supply system during the heating and summer periods. It is shown the possibility of operating a solid fuel heat generator with its power significantly less than the total heat load of the city's heating supply in several operating modes: during the heating period - for heating the return coolant at the inlet to the existing gas boiler house; in the summer period - for the needs of hot water supply in full; in the event of an emergency shutdown of a gas boiler house in winter - to maintain the viability of the heat supply system. The results of a calculation analysis of the operation of a 5,0 MW biofuel heat generator under different operating modes are presented. Heating the return coolant by 4...5 °C in winter, in addition to saving natural gas, prevents low-temperature corrosion of existing gas boilers. In the event of an emergency lack of natural gas supply, the combustion of wood chips ensures the production of thermal energy at the level of thermal losses of the heating network while maintaining the coolant temperature at least 3 °C at the calculated external air temperature. Thanks to the accumulation of thermal energy at night in the summer period in the volume of heating network pipes as a buffer tank, compensation for peak hot water consumption is provided with the available power of the solid fuel boiler house equal to the average load of the hot water supply system. When implementing a project to back up the heat supply system in Lutsk using a combined thermal scheme for connecting a solid fuel boiler house, an increase in the reliability and viability of the system and natural gas savings of 40,5% during a year of operation were achieved

An Experimental Study of a Grooved Aluminum-Ammonia Heat Pipe: The Effect of Tilting and Non-uniform Heat Transfer on Thermal Behavior

Much research has been done on aluminum/Ammonia heat pipes in recent years due to their wide applications in aerospace. Although lab-scale research regularly focuses on uniform heat input, heat generation is actually non-uniform in reality. Also, the circumferential temperature distribution and heat transfer coefficient (HTC) have not been reported yet. In this study, an axial grooved heat pipe, while the condenser state is kept constant, was experimentally tested to investigate the uniform and non-uniform heat modes, and the effect of tilted angle along with horizontal configurations were also examined in terms of circumferential temperature distribution and HTCs. Yet, a detailed explanation of the measured results is provided. For the same total heat load, it was found that the decreasing heat mode showed superior performance; the HTC at the evaporator is 72 % and 35 % higher than the increasing mode (the least performance heat mode) at 77 and 165 W, respectively. Upon inclination, the HTC in the evaporator is relatively independent of inclination. However, a sharp difference occurs in the condenser section where the HTC of the tilted configuration is more than twice higher than that of the horizontal configuration.

Numerical analysis for the design of a central air conditioning system for center of excellence

The temperature of the towing tank floor of the Center of Excellence in Marine and Offshore Engineering, Rivers State University needs regulation due to the high level of humidity during experiments. Since vapor evaporates from the towing-tank liquid column, the need for central air conditioning is timely. With the temperature regulated, it will help enhance the comfort of the students and improve the working condition of the staff and equipment. This is achieved by conducting a cooling load analysis, consistent with ASHRAE Guidelines, on the floor plan of the Laboratory building that provided useful information on the proper selection and sizing of fit-for-purpose air-conditioning equipment. Analysis revealed a total sensible and latent heat load of 59195.74 W with system capacity of 16.91TR (tons). Duct design utilizing the Velocity Reduction method resulted in a main supply duct length of 57m and flow are of 0.72m2 incorporating four branched ducts measuring 6m each in length and flow area of 1.05m2

Economic and Environmental Benefits of Heating of Poultry Houses with Geothermal Energy: A Case Study for Nevşehir Province of Turkey

In this study, as an example of the use of geothermal energy resources for the air-conditioning of animal shelters, the technical, economic and environmental gains that will be achieved in the case of heating a chicken coop with a total floor area of 480 m2 in Nevşehir province of Turkey in the winter months have been evaluated. For this purpose, a standard chicken coop with a length of 40 m, a width of 12 m and a height of 2.5 m and a capacity of 4320 chickens has been considered. The optimum indoor temperature for adult chickens is considered to be 22 °C. The total heat losses related to the different structural components of the considered standard house were determined. The annual total highest heat load for the poultry house was calculated as Qt = 197.32 kW. For geothermal resources suitable for house heating in the region, the amount of heat to be gained from the geothermal fluid to the house environment was calculated, taking into account the lowest physical properties (the lowest temperature Tgeo = 30 °C and the lowest flow rate mgeo = 30 m3/h). Since the amount of heat energy gained to the poultry environment with geothermal fluid (Qgeo=278.96 kW) is higher than the total heat losses (Qt = 197.32 kW) of the poultry house (Qgeo&gt;Qt), it can be used for poultry heating with geothermal fluid. In case the considered poultry house is heated with geothermal energy, a total of 45073 kg of fuel will be saved annually from LPG consumption and 42186.4 kg of diesel fuel consumption will be saved. If Diesel or LGP fuel is used instead of geothermal fluid for poultry heating, the annual total fuel cost will be 266 211.6 TL for LPG usage and 274 585.2 TL for Diesel usage. In case the considered house is heated with geothermal energy, 136 571.2 kgCO2-eq or 133 798.3 kgCO2-eq from the annual total greenhouse gas emissions will save compared to the use of LPG and Diesel, respectively.

Energy-economic-environmental analysis of a net-zero energy greenhouse with fan-coil units and hot-water pipes: Experiment and modelling

This study analysed the performance of a hot-water pipe (HWP) and fan-coil units (FCUs) in controlling microclimate conditions in a net-zero energy greenhouse (NZEG). The performance of a previously developed TraNsient SYstem Simulation (TRNSYS) model for the NZEG was enhanced to include a crop model and several HWP emission standards, and the improved TRNSYS model was used to analyse heating, ventilation and air-conditioning (HVAC) systems for different greenhouse sizes in the Republic of Korea. Further, an economic analysis was conducted. The model validation showed excellent agreement between the measured and simulated values, with Nash-Sutcliffe efficiency of 0.98. The presence of crop in the simulation model reduced the total heating load by 14.5 MWh and increased the cooling load by 4 MWh. The capacity of the FCU was increased as the outside temperature rose from 33.4[Formula: see text] to 36.4[Formula: see text] in summer, and the diameter of the HWP was decreased from 25A to 10A as the outside temperature rose from −21.7[Formula: see text] to −12.2[Formula: see text] in winter to maintain the greenhouse at the desired temperature of 15[Formula: see text]. Notably, the payback period was reduced by 9 years when the annual savings in heating energy costs and revenue from carbon trading were considered as a part of the net economic cash flow.

Experimental research and energy effectiveness analysis on chip-level two-stage loop thermosyphon system for data centre free cooling

The development of 5G technology has put forward new requirements for computing the abilities of chips, and chip power has also significantly increased. Consequently, the heat load of the rack will increase rapidly in the future. Traditional computer room air conditioning (CRAC) systems cannot satisfy the rack’s high heat flux dissipation requirements, and new cooling forms such as chip-level cooling should be adopted. In this study, a two-stage chip-level cooling system, which is pumpless and waterless, offers flexible and detachable installation based on practical requirements, was proposed. The cooling system removes heat from the chips to the outdoors via two thermosiphon loops, where the heat is first transferred to cold plates tightly attached to the chip surfaces, then transferred through heat exchangers attached to the rack side, and finally dissipated outdoors through air cooling. In this study, a two-stage chip-cooling system was constructed and tested in an enthalpy-difference laboratory. The effects of the liquid filling ratio on the thermal resistance, total temperature difference, and fluid flow pattern under different heat loads were investigated. Second, a heat transfer model for analysing thermal resistance networks was constructed, and the proportions of different types of thermal resistance were determined. Third, an energy-saving analysis of the system is established. The experimental results showed that at single chip heat load 200 W and total heat load 2 kW, the heat transfer temperature difference between chips and outdoors is less than 20 °C at extremely high energy efficiency (cooling load factor reaches 0.05 at outdoor temperature 40 °C), which makes it feasible for free cooling throughout the year in most Chinese areas. The annual PUE in Beijing using the proposed system is 1.15, which indicates a 30 % reduction of the total energy consumption of data centres.

Calorimetry measurement for energy balance and energy distribution in WEST for L-mode plasmas

This paper presents the energy balance of 602 pulses from four different experimental campaigns for the WEST tokamak. Different magnetic configurations have been studied, with lower single null (LSN) and upper single null (USN) configuration with deuterium or helium plasmas. The energy balance is closed with an imbalance of about 5% of the total injected energy for most of the campaigns and for different magnetic configurations. The distribution over the whole machine is shown, with the outer first wall receiving most of the energy due to its large surface area with about 30% of the total heat load, and the divertor with 25% due to the heat loads deposited by the convected power in the scrape-off layer (SOL). Finally, the tomography inversion of the bolometry measurement allows us to disentangle the contribution of the radiated and convected power in the energy absorbed by each type of plasma-facing component. We show that in the USN configuration about 63% of the available energy in the SOL is deposited in the upper divertor (UDIV) through convected heat loads, while in LSN this value is spread over the lower divertor with 45% and the baffle and UDIV with about 10% for both.

Dynamic Modeling of a Solar-To-Hydrogen Flexible High Temperature Steam Electrolysis Plant

Sustainble hydrogen production for use as a renewable combustible fuel and clean chemical feedstock is an important objective as the world moves towards a renewable energy future. High temperature steam electrolysis is a promising hydrogen production technology due to its reduced electric input that is offset by heat input into steam generation and steam superheating. An option to provide this heat is to use concentrating solar thermal technology that can sustainably provide heat input while renewable electricity is used for the electrolysis reaction. In this work, a solar-to-hydrogen high temperature steam electrolysis plant is designed and dynamically modeled, showing continuous hydrogen production by utilizing supplemental heating and efficient recuperative heating from the electrolysis product streams. Through this design, over 90% of the required heat input for the process can by met by a combination of solar and recuperative heat. Additionally, the plant can flexibility operate by ramping down hydrogen production and through flexible heat integration, which intelligently integrates solar heat based on solar conditions. Smooth operation with flexible hydrogen production is demonstrated which decreases electrical input during on-peak grid times and also decreases the total supplemental heat load over the course of a day from 26.1% to 24.5%. In addition, by using flexible heat integration, the plant can increase its solar heat usage by 4.1% relative to a base case. Both options for flexibility show efficient use of solar thermal energy to sustainably and continuously produce hydrogen.

Preparations of QWR superconducting cavities for beam commissioning

Quarter-wave resonator (QWR) cavities are prepared for beam commissioning. RF conditioning is performed for each QWR cavity. The total heat load, including static and dynamic heat loads, is measured for each cavity. The helium pressure fluctuation is reduced by changing the flow rate, supply pressure, return pressure, cryogenic valve control, etc. The cavity pressure is monitored during RF preparation. The amplitude and phase of the QWR cavity are stably controlled for beam commissioning.

Thermal Performance Evaluation of TIM Combined with Residential Windows in Different Climatic Regions in Iran

Windows play a significant role in the increase and loss of heat from the building envelope and determine the quantity, quality, and distribution of daylight. A strategy that involves incorporating transparent insulating materials into a double-glazed window offers the potential to provide combined improvements in thermal and daylighting performance. The thermal properties of transparent insulation materials in windows depend on various factors, such as the type of insulation material, thickness, geometry and insulation structure, location, and orientation of the window, among others. The aim of this research is to optimize three criteria: "thickness," "location of transparent insulation relative to window layers," and "direction of the wall with transparent insulation of the building window." The goal is to minimize thermal loads and reduce energy consumption in residential buildings. To achieve this, a real model was selected, and Design Builder software was used to measure the "heating load," "cooling load," and the sum of these two loads as the "total thermal load" for all three criteria in three cities of Iran with different climates: Tehran (moderate climate), Ahvaz (warm climate), and Tabriz (cold climate). The results of the research showed that for the city of Tehran, 3-inch insulation in the middle of the double-glazed window and the south front is optimal. For the city of Tabriz, 5-inch insulation on the inner surface of the window and the western front is optimal. And for the city of Ahvaz, 3-inch insulation on the outer surface of the window and the eastern front is optimal. It is worth noting that the annual heating load and total annual heating load for all three criteria have the highest values in Tabriz city. Therefore, it is recommended to use HSNPS insulation in transparent windows to reduce energy consumption in Tabriz (cold climate).

Unsteady conjugate heat transfer simulation of wall heat loads for rotating detonation combustor

Rotating detonation engines (RDEs) are the most promising pressure-gain combustion devices, but their long-duration operations are hindered by the harsh thermal environment inside the chamber. This study analyzes the instantaneous and average heat loads on chamber walls of RDEs based on the newly developed unsteady conjugate heat transfer (CHT) OpenFOAM solver named multiRegionBYRFoam. To enhance accuracy in predicting heat transfer characteristics compared to decoupled simulations focusing solely on fluid or solid behavior, three-dimensional CHT simulations are conducted for a premixed H2/air annular RDE coupling the detonation simulation with heat conduction in both inner and outer chamber walls. The transient time evolutions of wall heat flux in RDEs are numerically captured for the first time and agree well with experiments. The calculated peak wall heat flux is 1.98 MW/m2 at the inner wall and 2.63 MW/m2 at the outer wall when a single detonation wave propagates with a mass flow rate of 0.227 kg/s. By investigating the influence of inlet flow conditions and detonation modes, valuable guidelines on designing efficient thermal management systems for RDEs are obtained: larger mass flow rates and multi-wave modes result in higher average wall heat flux; the heat flux at the outer wall exceeds that at the inner wall while both walls require effective cooling for gas turbine engines with a rotating detonation combustor. Furthermore, a novel heat transfer model for RDEs is proposed based on a thermal operation map depicting total heat transfer rates to describe the nonlinear impact of mass flow rate and number of detonation waves, which can be employed to predict total wall heat loads under specific operation conditions of RDE.

THE DESIGN OF THE POWER SUPPLY CURRENT LEADS TO A HIGH-TEMPERATURE SUPERCONDUCTING ELECTROMAGNET

The paper presents a theoretical and experimental analysis of thermal conditions imposed on the power supply conductor for an HTS YBCO-type high magnetic field electromagnet. For thermal stability during the operation of the electromagnet, it is essential to lower the heat flux from outside the system. The heat from the surrounding environment to the HTS winding is limited by using an adequately sized cryogenic system and the proper design of the current leads. The HTS winding and current leads are cooled with a two-stage GM cryocooler. If the power supply conductor's conductive heat flux exceeds the cryocooler’s heat load, the temperature of the HTS winding will increase, and system instability may occur. The power supply conductors are of two types: copper conductors and mixed HTS conductors. This work analyzes HTS conductors and junctions of HTS tape with copper terminals and their contribution to the cryocooler’s total heat load. Using HTS conductors reduces Joule heat when current passes through them (approx. 300 A) and the conductive heat flux to the HTS windings. Resistance for various soldering alloys was experimentally evaluated to evaluate the Joule heat of the junctions between HTS conductors and copper terminals.

Experimental and numerical investigation of integrating energy recovery ventilation into a thermodynamic-potential-based passive dehumidification system using renewable energy

To decrease the latent heat load of the air-conditioning system in residential buildings, we proposed a passive dehumidification and mechanical ventilation system that integrates energy recovery ventilation (ERV) into a passive dehumidification and solar collection (PDSC) system that can intelligently regulate the indoor hygrothermal environment, referred to as the PSE (PDSC & ERV) system. Field studies were conducted by monitoring the indoor temperature and humidity changes in the operating conditions using various systems. With the PSE system, the absolute humidity difference between the indoor and outdoor air was the most significant, and its ability to maintain a stable indoor relative humidity was the most remarkable compared with other systems. The PSE model had the lowest latent and total heat load compared with the exhaust-only ventilation model equipped with a standard insulated envelope without moisture adsorption and desorption function. Regression analysis showed that the higher the outdoor temperature, absolute humidity, relative humidity, and solar radiation in summer, the more significant the PSE system's latent heat load reduction effectiveness. Linear correlation between absolute humidity and energy-saving performance was the most evident, with a coefficient of determination as high as 0.98, illustrating the suitability of PSE systems for hot and humid areas.

Experimental evaluation of direct-to-chip cold plate liquid cooling for high-heat-density data centers

Owing to the dramatic increase in IT power density and energy consumption, the data center (DC) sector has started adopting thermally- and energy-efficient liquid cooling methods. This study examines a single-phase direct-to-chip liquid cooling approach for three high-heat-density racks, utilizing two liquid-to-air (L2A) cooled coolant distribution units (CDUs) and a combined total heat load of 128 kW. An experimental setup was developed to test different types of CDUs, cooling loops, and thermal testing vehicles (TTVs) for different operating conditions. IR images and the collected data were used to investigate the effect of air recirculation between cold and hot aisle containments on the CDU’s performance and stability of supply air temperature (SAT). Three different types of cooling loops (X, Y, and Z) were characterized thermally and hydraulically. Results show that Type Y has the lowest cold plate thermal resistance and pressure drop, among others. In a later test that included a single rack at a heat load of 53 kW and a single CDU, the heat capture ratio for fluid was found to be 94%. Experiments show that using blanking panels on the back of the racks limits hot air recirculation and maintains a steady SAT in the cold aisle. Finally, the CDU performance was evaluated at a high heat load for the three racks at 128 kW, and the average cooling capacity of the units is 58.6 kW, and the effectiveness values for CDU 1 and CDU 2 are 0.83 and 0.82, respectively.