Cold Air Distribution Research Articles

Analysis of cooling load calculations using AHU in swimming pools (indoor pools)

AC or Air Conditioner is one of the most widely used mechanical devices in Indonesia. A machine device that functions as an air conditioner so that the indoor air temperature is comfortable, healthy, and has the humidity required by the occupants. Air freshening systems or ACs are increasingly becoming a necessity for urban communities, whether in homes, office buildings, apartments, hotels, swimming pools, hospitals, and even in lecture rooms. The indoor swimming pool measuring 40 x 11 x 3.5 m is located in the apartment So it is uncomfortable for swimmers. Thus, it is necessary to design using an AC system so that the temperature in the swimming pool is cool and comfortable for swimmers. The planning methodology starts by determining data on the indoor swimming pool in apartment AC used. From the analysis results, the cooling load was obtained at 411.5 kW, including a sensible load of 397.66 kW and a Latin load of 13.85 kW, the refrigerant used by the engine was R134a, the compressor power was 81 HP, while the COP was 6.8. So that the indoor air is evenly distributed comfortably, the indoor cold air distribution system uses an AHU (Air Handling Unit) system, capacity of 1900 m3/hour. 2 AHU Units, Blower Power 3 kW

Investigating thermal performance and energy efficiency in under-floor air distribution data centers: A case study

This study conducted on-site measurements of air temperature and airflow velocity at the cold aisle outlet, combined with infrared imaging, to derive optimized layouts for rack servers. It was found that installing blind plates effectively improves the uniformity of cold air distribution within the racks, as indicated by the temperature and airflow velocity at the server inlet and outlet under both blind and non-blind plate conditions. Finally, thermal performance indicators (i.e., SHI, β, RHI, RCI) and Reynolds number were used to assess the thermal performance of the data center, while energy efficiency indicators (i.e., PUE, WUE, CUE) were employed to evaluate its energy efficiency. The results revealed that the cold aisle has less air distribution at both ends and is more concentrated in the middle. It is advisable to position high-power servers in the middle racks and place racks with relatively lower power at the front and rear ends to ensure effective heat dissipation of the servers. The installation of blind plates can effectively enhance the uniformity of airflow within the racks and improve server cooling. Among the tested racks, 16 out of 17 exhibited low temperatures (RCILO) below 90%, indicating heat loss and energy waste. The PUE value of the data center is 1.19, and the CUE value is 0.77.

Investigating photovoltaic module performance using aluminium heat sink and forced cold-air circulation method in tropical climate conditions

Solar energy is seen as a good option to replace fossil fuels in electricity generation. However, PV panels produce unnecessary heat energy during power generation which increases the temperature and affects the efficiency of PV cells. This article investigates the performance of PV modules using aluminum heat sinks and forced air cooling techniques. A cooling circuit configuration connecting a 6-inch pipe plenum with 5 T-shaped pipes is installed under the solar cell to provide better cold air distribution to the PV panels. The study was conducted on-site and in real-time conditions in a public hospital with high energy consumption as it operates continuously throughout the year. The combination of the two methods has optimized the performance of solar panels in terms of efficiency and electrical energy output. The average electrical efficiency of the studied PV panels is 17% and is very close to the PV module efficiency of 19.38% under standard test conditions (STC). The actual energy yield recorded for the installed PV panel is 12.35% higher than the estimated solar energy output under nominal operating cell temperature (NOCT) conditions. The results of the study show that solar energy generation can be optimized by considering the design, use of materials and proper cooling methods even when using the same solar panel.

Determination of Variability in Ambient Conditions During Cold Storage of Aronia Fruits

In this research, temperature and relative humidity in a cold store with an evaporative cooling system were investigated during one-month cold storage of Aronia melanocarpa Nero fruits. Ambient temperature and relative humidity were measured by sensors at 36 points for different levels (top, medium and base level). The research was carried out in accordance with the randomized plot design for the purpose of storing Aronia melanocarpa in a cold store at +3oC for 1 month. The results were evaluated by using variance analyses and descriptive statistics. In addition, spatial variability maps were created for evaluating of temperature and relative humidity variation at different levels. Variation of the temperature was determined between 3.40oC and 5.32oC for top level, 3.80oC and 5.49oC for middle level and 3.92oC and 5.51oC for base level at 3oC storage temperature. Coefficient of variations was determined as 11.47% for top level, 11.48% for middle level and 7.10% for bottom level for temperature. The relative humidity values were changed between 74.00% and 88.09%. Mean coefficient of variation of the relative humidity varied between 3.22% and 4.43%. According to the results; distributions of the temperature and relative humidity for different levels were not uniform. Reason of high variability between measurement of the temperature and the relative humidity for different levels in the cold store was the distribution of the cold air. The cold air was ventilated by an evaporator and distributed according to the design of the cold store (dimensions, shape, and materials) and placement of fruit cases. Different storage conditions were determined at different levels in the cold store during storage of Aronia fruits in this research. In addition, there is generally one temperature/relative humidity sensor located back of the door inside the cold store used to control the cooling system. Measurement of the temperature and relative humidity from one point in a cold store is not enough to give an idea about the ambient conditions of the cold store. When storing agricultural products, the use of more temperature/relative humidity sensors in the cold store will enable the actual situation of the temperature and relative humidity values to be taken into account to control the operation of the cooling system. Additional cold air distribution systems such as ventilator, air curtains and placement of fruit cases may help to improve air distribution and decrease the spatial variability of the storage conditions in the cold store.

Effect of controlled cold air distribution on temperature profile and phase transformation of wire loops in the Stelmor air-cooling process

Wire rods produced by the Stelmor air cooling process were found to have the problem of microstructure non-uniformity. The proper distribution of cold air from the nozzle of the plenum chamber can adjust the convection heat transfer intensity at the different positions of wire loops, and further control the dynamic distribution of temperature and phase transformation on wire rods. A three-dimensional mathematical model incorporating the turbulent flow of air, heat transfer and the JMAK phase transform model in the Stelmor process has been developed. Two types of air nozzle were applied in our study, and Type B nozzle which blocked the center portion applied more air to the side region of wire loops than the Type A nozzle. Compared to the unblocked nozzle, the type B nozzle can effectively reduce the temperature difference between the low dense zone and high dense zone on the wire loops from 69.7 K to 18.4 K. The simulated temperature results of wire loop agreed well with the measured one in the industry trials. The present study has demonstrated that these models can be useful tool for optimizing cooling condition in the Stelmor process and predicting the temperature profile and microstructure evolution of the wire rods.

D-24 低温冷風空調システムを活かした東京電力豊島支社のリニューアル : 第3報 アンケート調査と実測結果

D-24 低温冷風空調システムを活かした東京電力豊島支社のリニューアル : 第3報 アンケート調査と実測結果

DESIGNING OF A VARIABLE VOLUME COLD STORE

Cold stores do not work for all time as full loaded during storage period. There isalways empty space when cold store is not fully loaded. Unnecessary energy isconsumed because this empty volume must be cooled even there isn’t any storedagricultural product. In this study a system was developed to adjust cold storevolume according to the amount of stored agricultural product. Therefore, effectivevolume of the cold store where agricultural product stored will only be cooled andenergy saving will be established. In addition, better cold air distribution will beestablished in the cold store and the quality of product will also be better preserved.Developed system is a moving wall-door system located inside of the cold store. Itcan be moved automatically. Sliding-wall door system can be moved by anelectrical engine on a rail located at side walls. Leakage of cold air is prevented bya silicone seal balloon. The silicone seal balloon is located all-around of the slidingwall-door. The sliding wall change volume of cold store due to amount of storedproduct. Sliding wall-door system is a new approach for manufacturing of coldstorage. This system will not be used only for new cold stores, but also can be usedfor old cold stores. Energy saving is expected by using developed system in coldstores. Submission of Petit patent for this developed system was approved byTurkish Patent Institute.

Numerical Simulation Analysis of Cold Air Distribution System

This paper based on an actual project as an example, researching the application of cold air distribution system by using the numerical simulation method. By using Fluent software to establish a three-dimensional physical model, simplificate the physical model, establish proper tuyere model, choose the appropriate turbulence model, select the appropriate boundary conditions. Then simulate indoor airflow organization, get the distribution of temperature field, velocity field in the working area, and evaluate the comfort in the working area. Though the research, this paper provides the appropriate air distribution which is the upper supply air and on opposite side bottom exhaust air. This paper though the numerical simulation concludes that adopts the appropriate air distribution could meet the requirements of indoor thermal comfort.

Experimental study of solving thermal heterogeneity problem of data center servers

Desirable thermal management of data center requires uniform temperature distribution along the servers. Hot air recirculation and cold air bypass in data center leads to non-homogeneous cold air distribution along the servers of the racks which may lead to heterogeneous temperatures distribution along the servers. The present work aims to experimentally study the possibility of controlling these heterogeneous temperature distributions by controlling the cold air flow rates along the servers. A physical scaled data center model was used to conduct this investigation. The effectiveness of thermal management of the servers racks of the data centers has been expressed in terms of intake, rare and surface temperature distributions along the rack servers and the supply and return heat indices (commonly symbolized as SHI and RHI; respectively). Excessive tests were firstly performed under uniform servers fans speed (uniform air flow rates through the different servers). Then the air flow rates distributions along the racks servers has been changed by regulating the server’s fans speeds using different schemes of fans speeds regulations at different data centers power densities. It is concluded that a uniform increase of server’s flow rate from the bottom to the top of servers rack cabinet provides (i) the lowest temperature at both cooling aisle (around 10%) and exhaust aisles (around 5%), (ii) the best uniform surface temperature of all rack servers (as the standard deviation is reduced from 10 to around 2), and (iii) the best values of thermal management metrics (SHI and RHI) typically SHI is reduced by around 20% while RHI is increased by around 3% to approach the targeted values; 0.1 and 0.9, respectively.

Application Study of Cold Air Distribution System

This paper briefly introduced the cold air distribution system principle and characteristics. Apply the simulation software to simulate air distribution and thermal environment of cold air supply room. Adopt Effective Draft Temperature (EDT) and Air Diffusion Performance Index (ADPI) to evaluate indoor thermal comfort.

Practical Use of Fluctuating Breeze System with Cold Air Distribution : Development of Fluctuating Breeze System and Evaluation by Field Test

Practical Use of Fluctuating Breeze System with Cold Air Distribution : Development of Fluctuating Breeze System and Evaluation by Field Test

Thermodynamic analysis of air cycle refrigeration system for Chinese train air conditioning

The air cycle refrigeration system used in Chinese train air conditioning engineering is investigated. The effects of possible parameters affecting system performance are examined through sensitive analysis of the thermodynamic model. The results show that, the pressure ratio should be in the range of 2-2.5, the COP will be in the range of 1-1.2, and the cold air distribution system can be used. To increase the COP, higher efficiencies of compressors, expanders and heat exchangers are expected.

変動微風空調システムの実用化に関する研究 : 変動微風が心理量および生理量に与える影響

Cold air distribution system with fluctuating airflow creates the feeling of coolness by generating airflow over the human body. The airflow is set as a fluctuating airflow within a range in which the human body does not feel uncomfortable. We confirmed from the experiments using test subjects that the sensation of comfort was maintained with a fluctuating airflow in a room. It is in a room condition that wind velocity of 0.4 to 0.8 m/s, temperature of 28 to 29 degree C 40%RH, a clothing to 0.4 to 0.6 clo and an activity level of 1.1Met.

Performance evaluation of an innovative fan-coil unit: Low-temperature differential variable air volume FCU

An innovative low temperature differential variable air volume fan-coil unit (LTD-VAV FCU) was developed to improve the defects of variable air volume (VAV) and cold air distribution energy-saving technologies. A test bench and procedures according to its unique air supply features were established to investigate the energy-saving and IAQ improving potential experimentally. The experimental results of the prototype indicated the supply air volume can be continuously varied between 0.09 m 3/s (200 CFM) and 0.38 m 3/s (813 CFM), controlled by the bypass damper giving an air supply/air return temperature difference from only 2.30 to 8.09 °C. The effect of reducing the supply/return air temperature differential not only makes people feel comfortable, but also improves the cold draft and condensing at the outlet generated by ordinary air supply method. In addition, continuous capacity variations range from 0.45 kW (383 kcal/h) to 5.29 kW (4550 kcal/h) rendering to achieve the effect of comfort at a stable indoor thermal condition. Moreover, the temperature difference of chilled water ranges from 0.42 to 5.05 °C, the chiller plant not only can be unloaded at a low temperature difference to enhance energy-saving, but also complement other areas for multi-area application.

Behaviour of inclined jet on room cooling

Cold air distribution systems are increasingly attractive when used with the ice storage systems as they require less operating and capital costs. However, an important issue in design and application of cold air systems is the effect on occupant comfort. In this investigation air circulation and temperature distribution in a room have been studied for different orientations, velocities and sizes of jet of conditioned air for a given vertical location of air inlet and outlet on opposite wall. Navier–Stokes equations and energy equation in two dimensional rectangular cartesian co-ordinates have been solved by control volume method. It has been observed that the performance of the cooling improves with the increase of jet dimensions. A drastic and remarkable change has been observed in the flow pattern at critical Gr, beyond which it leads to oscillatory flow. It has also been observed that if the conditioned air enters at an angle of 10° with the horizontal through the inlet of size 0.2 m, laminar non-oscillatory flow can be sustained for the largest range of Gr=10 7 at Re=2000.

Cold-Air Distribution Comparison for Four Supply Air Diffusers

Cold-air distribution (CAD) with ice storage systems can potentially lower operating and first costs when compared to conventional heating, ventilating, and air-conditioning systems. One concern fo...

Numerical studies of airflows induced by mechanical ventilation and air-conditioning (MVAC) systems

Indoor air flows induced by mechanical ventilation and air-conditioning (MVAC) systems are simulated by the technique of computational fluid dynamics (CFD). Examples are taken to illustrate the capability of the technique. These include the evaluation of basic ventilation system designs, ventilation systems in an enclosed car-park, spot cooling system, air-conditioning system with chilled ceiling, cold air distribution system, effect of casual heat gain on the air diffuser induced air flow and the underfloor air supply system. Evaluation of the performances of the mechanical systems in those buildings are performed. Physical experiments in air-conditioned spaces reported by Sakamoto and Matsuo; and by Murakami and Kato are also simulated to assess how good are the predicted results.

Flow and Separation Characteristics of Three-dimensional Negatively Buoyant Wall Jets

This paper reports a study of the behavior of cold air jets, specifically three-dimensional, incompressible, negatively buoyant, turbulent wall jets, and their separation from horizontal surfaces. With a cold-air distribution system, both the supply air temperature and flow rate are lower than in conventional systems for the same cooling load. The cold air is supplied to a zone at temperatures between 39°F and 49°F (3°C and 9°C) instead of the conventional 55°F (13°C). As the building's ventilation and cooling airflow supply temperature and flow rate are reduced below the conventional values, indoor thermal environment considerations become increasingly important. An analysis using integral forms of the momentum and energy equations is presented for determination of the separation point of buoyant turbulent wall jets. The analysis shows that the separation point is a function of the outlet Richardson number in addition to the geometry of the outlet diffuser or nozzle. Also reported in this paper is an experimental investigation of the mixing and separation of three-dimensional buoyant turbulent wall jets of air discharging into a large room. Velocity and temperature difference profiles and half-width growth rates for these jets are presented. The separation distances are also measured, and compared to the predicted results.

A-21 (その4)実建物における冬期空調性能実績と室内環境評価 : 氷蓄熱用低温冷風空調システムの開発

A-21 (その4)実建物における冬期空調性能実績と室内環境評価 : 氷蓄熱用低温冷風空調システムの開発

95/01832 Control strategies and energy consumption for ice storage systems using heat recovery and cold air distribution

95/01832 Control strategies and energy consumption for ice storage systems using heat recovery and cold air distribution