Air-cooling Device Research Articles

Continuous operating elastocaloric air-cooling device

<p>Elastocaloric cooling has shown significant potential as an alternative to traditional vapor-compression technology because it relies on nonflammable, non-toxic, and zero-global warming potential solid refrigerants (usually NiTi and TiNi-based shape memory alloys). However, the uniaxial loading mode commonly used in existing elastocaloric cooling devices is often accompanied by a lower operating frequency. Additionally, using water as the heat exchange medium presents challenges in further cooling the air with cold water. These issues will hinder the application of this type of refrigerators in space cooling scenarios. Here, we report a continuous operating tension-based elastocaloric air-cooling device that utilizes the bundles of NiTi wires. The driving mode based on the cam structure realizes the alternating loading-unloading cycle of multiple NiTi bundles, facilitating continuous the cooling process. Our air-cooling device achieves a temperature decrease of 4.4 �� in continuous air flow and provides a cooling power of 21 W. These results demonstrate the possibility of applying elastocaloric technology in space cooling and provide a technical reference for designing household air conditioners using this technology.</p>

Method development for determining the energy-efficient mode of air-cooling devices’ operation

When ensuring the normative limit of the heat of the gas transmitted to the main gas pipelines by means of air cooling devices of the gas transmission compressor station, the modes of parallel operation of the fan motors of the air cooling device system are considered. At the same time, a comparison was made of methods for adapting air cooling devices to factors affecting energy-efficient operating modes. As a result, based on a mathematical model of the combustion operating mode through a gas-air cooling device, the possibility of regulating the engine speed and increasing the energy efficiency of the system, taking into account seasonal and temperature changes, is shown. The main parameters for saving energy sources are introduced into the technological processes of gas compression and cooling.

Comparison Analysis of Liquid and Air-cooling Systems for GPU

Abstract: In order to increase reliability and prevent early failure, heat produced by electronic components and circuits must be drained. Heat sinks, fans, and other air-cooling devices, as well as alternative computer cooling methods like liquid cooling, can all be used as heat dissipation techniques. Here the paper's main focus is on a numerical analysis of temperature distribution in a GPU scenario with various input velocity circumstances, including v = 1 m/s, 3 m/s, and 5 m/s. Air and water are the two distinct fluids employed in this investigation to cool the graphics card. An analysis of the fluid flow and heat transfer simulation of a desktop graphics card heat sink is conducted using the CFD software ANSYS Fluent. According to the findings, cooling with water was 10% more effective than cooling with air. The outcome also shows an inverse correlation between the graphic card chip's intake velocity and temperature. The rate of heat transfer to the heat sink increases as the inflow velocity rises which is helped by the convection.

Randomized cross-over study investigating the tolerability and side effects of an intra-oral air-cooling device compared to ice in healthy volunteers

Oral cryotherapy (OC) is a common preventive treatment of oral mucositis (OM) and is recommended in international guidelines. Ice and air OC have previously been shown to result in temperature reductions of 8.1–12.9 °C, and 14.5 °C, respectively, in healthy volunteers. However, no direct comparison between these two modalities has been performed. The primary aim was to investigate the tolerability and side effects of air OC using an intra-oral air-cooling (IOAC) device compared with ice OC. The secondary aim was to evaluate the temperature reduction in the mouth for the two respective methods. Cross-over study with randomization to order of treatment, in 15 healthy volunteers. We evaluated the self-reported intensity, frequency, and discomfort for 13 pre-defined side effects used in previous studies. All participants were able to complete both OC sessions, although one participant required reduced airflow in the air OC arm. The subjects reported more discomfort from being cold, having sensitive teeth, and numbness in the ice OC group, while they reported more discomfort from swallowing when subjected to air OC. No significant difference in the median temperature reduction was detected in the two modalities, except for the dorsal posterior part of the tongue where temperature reduction was larger in the ice OC group. We found that oral cooling using a new IOAC device was tolerated and seems to be safe in healthy volunteers.

Influence of the purity of water-oil emulsions on the degree of contamination of the surfaces of finned tubes of air coolers

The existing technologies for cleaning finned bimetallic tubes of air-cooling devices and methods for control the contamination of the surface of aluminum alloys are analyzed in order to identify the disadvantages of the cleaning methods used in the production of finned tubes. A quantitative rapid assessment of the finned surface cleaning is obtained. Keywords: finned surface, contamination, cleaning, alkaline solution, finned bimetallic pipes, air cooler, control. alex@bgutmo.ru

Experimental Investigation of the Heat Transfer Characteristics and Operation Limits of a Fork-Type Heat Pipe for Passive Cooling of a Spent Fuel Pool

A fork-type heat pipe (FHP) is a passive heat-transport and air-cooling device used to remove the decay heat of spent nuclear fuels stored in a liquid pool during a station blackout. FHPs have a unique geometrical design to resolve the significant mismatch between the convective heat transfer coefficients of the evaporator and condenser parts. The evaporator at the bottom is a single heat-exchanger tube, whereas the condenser at the top consists of multiple finned tubes to maximize the heat transfer area. In this study, the heat transfer characteristics and operating limits of an FHP device were investigated experimentally. A laboratory-scale model of an FHP was manufactured, and a series of tests were conducted while the temperature was varied to simulate a spent fuel pool. As an index of the average heat transfer performance, the loop conductance was computed from the measurement data. The results show that the loop conductance of the FHP increased with the heat transfer rate but deteriorated significantly at the operating limit. The maximum attainable heat transfer rate of the unit FHP model was accurately predicted by the existing correlations of the counter-current flow limit for a single-rod-type heat pipe. In addition, the instant heat transfer behaviors of the FHP model under different temperature conditions were examined to interpret the measured loop conductance variation and operating limit.

Experimental and computational study of using nanofluid for thermal management of electronic chips

The compact equipment, area restriction for air-cooled devices, and thermal management of microchips have attracted the attention of researchers concerned with superior liquid cooling systems. During the present study, the impact of using nanofluids for cooling a chip was carried out experimentally and numerically. The experiments were conducted to validate the CFD model. Then the CFD model was applied for examining the impact of nanofluid concentration, and coolant flow rate on the thermal-hydraulic characteristics of the heat sink. CuO-water nanofluid was used with five different nanoparticle volume fractions of 0.5, 0.86, 1.5, 2.25, 3.5 and 5 vol.%. The developed CFD model was validated with the obtained experimental results and with results of different researchers, which showed good agreement. The results showed that for the investigated electronic chip with an area of 5 cm by 5 cm and dissipated power of 130 W, an enhancement of 8.1% in thermal conductance was noticed when using nanofluids as compared to water for the studied operating range. The overall thermal hydraulic performance of using nanofluid is found to accomplish higher value of 1.47 at nanoparticle volume fraction of 5% of CuO and Reynolds number of 800.

Projecting global water footprints diminution of a dew-point cooling system: Sustainability approach assisted with energetic and economic assessment

In the coming decades, a large portion of the world population is expected to embrace urbanization. The demand for thermal comfort in populous and congested urban centres, especially in developing countries across the globe, is expected to rise many folds. Alternates to conventional air-cooling systems are water-based evaporation cooling. Recently introduced efficient multi-stage indirect evaporative cooling using the Maisotsenko(M)-Cycle has shown success with improved performance by theoretically reaching the dew-point of the incoming air. However, the impact of large-scale use of such cooling devices shall inadvertently leave huge strains on the urban useable water resources. On the other hand, cooling, as usual, is not sustainable with the global demand for air cooling units shall grow many folds up to 5.0 billion units over the next decade compared to currently 1.3 billion in service units.Alternates of high electricity consuming air cooling, such as Maisotsenko cycle based devices are part of the solution only if the water impact can be brought to minimal in an efficient manner. A key development in this regard is the utilization of water recovery systems from waste air streams leaving air coolers. A few studies and models have shown their successful working and predictions. This paper initially analyzes the global impacts of air-cooling devices using the commercially available product designed to work on the Maisotsenko cycle. Moreover, the impact of these devices on the global scale in terms of utility as well as their water footprints are estimated. The results produce a grim picture since most favourable zones/regions in the globe for indirect evaporative cooling are also labelled as high on the water stress index. Secondly, global assessment of water recovery unit in terms of reduction in water footprint and combined cooling and recovery system Energy Efficiency Ratio (EER) are also assessed. Based on the assessments and predictions of global economic parameters, a wholesome Levelized Cost of Electricity of combined air cooling and water recovery system is estimated for each zone across the globe favourable for the Maisotsenko cycle based air cooler.The hypothesis postulate that the global projections of the energy-efficiency-ratio should be improved while diminishing its water footprints at a lower Levelized cost. The prime purpose of the research is to evaluate the technological advancement presented in the commercial M50 air cooler for energetic, economical, and water-related indicators with the consideration of global projections in similitude to the social contexts of the region. Our hypothesis is verified with our assessment and the principal results have suggested that recovering the water from M-50 cooler, a commercially available device working on M-Cycle, yields in the reduction of specific water usage per ton of air cooling by ~63% while the EER improved by ~26% as compared to the conventional air cooling and the Levelized Cost of energy is 0.014 USD/kWh which is much lower than the conventional air conditioning systems.The findings of this article have concluded that proposed technological advancement has better performance indicators, suiting the complicated local context, and it is suggested/recommended to the governments (especially the Middle East, South Asian, Central Asian, North African, and Australia) to include such natural air coolers (particularly M-Cycle machines) in the national energy efficiency plans to meet the global sustainability targets of United Nations.

Improvement of Efficiency of Air Cooling Devices By Creation of Independent Modules with Evolvent Profile Composition of Finned Tubes


 
 
 An analysis of the composition of the heat-exchange equipment at the petrochemical plants reveals that nominally more than 30% (and by weight about 50% of the total equipment) is heat-exchange equipment, including air-cooled units requiring replacement and reconstruction as a result of the end of their service life or corrosion erosion wear. Therefore, work aimed at improving the effectiveness of ABO is relevant. The existing problem of reducing the efficiency of air cooling in hot calm weather is compounded by the need for short-term humidification using a humidifier mounted directly behind the fan wheel when the air enters the diffuser. This dramatically increases the processes of corrosion and the formation of deposits on the surface of finned tubes (scale, fluff and dust). We have carried out a set of computational and experimental studies to evaluate the thermal efficiency of small-sized ABOs of various designs using a universal experimental industrial bench. The results of studies have established that vertical-cylindrical ABO designs are more energy-efficient and less metal-intensive compared to typical horizontal ones and allow for the influx of cold atmospheric air to the ABO inlet during the hot season.
 
 
 
 Keywords: air cooler; heat transfer coefficient; thermal efficiency; design of a vertical cylindrical air-cooling apparatus; involute profile layout
 
 
 
 
 

РЕКОНСТРУКЦИЯ СОЕДИНЕНИЯ ТРУБ С ТРУБНОЙ РЕШЕТКОЙ В АППАРАТАХ ВОЗДУШНОГО ОХЛАЖДЕНИЯ

The article analyzes the types of pipe connections with a pipe grid in air-cooling devices. Based on this analysis, it is proposed to change the design of pipe fastening instead of rolling to
 tightening nuts in ABO-103/1-2 of the sulfuric acid alkylation unit

ANALYSIS OF ECONOMIC EFFICIENCY OF USING FLAT-OVAL TUBES WITH INCOMPLETE FINNING IN CONDITIONS OF NATURAL DRAFT

The efficiency of air coolers, working in free convection mode is considered. The expediency of installing an exhaust tower over the heat exchange surface of the air cooler and its transfer to the mode of natural draft has been established. The possibility of using flat-oval tubes with incomplete finning in the designs of air-cooled devices with natural draft is noted. Variant calculations of the aircooling device on the basis of the most widespread in the market of Ukraine finned tubes in which the quantity of air necessary for maintenance of thermal power is provided only by an exhaust tower are carried out. Comparisons of the results of calculations show that the best technical and economic indicators have a variant of the air cooler based on flat-oval tubes with incomplete finning. The amount of capital costs for the manufacture of air cooler based on flat-oval tubes with incomplete finning is 47% less than the heat exchanger based on bimetallic tubes with rolled spiral finning and 2 times cheaper than the option of aircooler based on tubes with welded spiral fins or oval pipes with oval finning.

Primary evaluation of an air-cooling device to reduce oral mucositis: a pilot study in healthy volunteers

Oral mucositis is a common side effect of chemo and radiotherapy causing painful ulcers in the oral mucosa. One of the preventive treatments recommended in international guidelines is oral cryotherapy (OC). Randomized clinical trials on OC have used ice and ice-chips to cool the mouth, but this cooling method can be difficult for the patients to tolerate. Studies have shown that OC with ice for a period of 60 min reduces the oral temperature by 12.9 °C. The aim of this pilot study was to evaluate the temperature reduction and tolerability of OC using an intra-oral air-cooling (IOAC) device in healthy volunteers. Twelve healthy volunteers, mean age 35.4 years, were included in the study. They were treated with OC using the IOAC device for 60 min. Measurements of temperature were obtained at baseline, 5 and 60 min using a FLIR® C2 camera. After the OC session, tolerability and adverse events were documented using a questionnaire. All participants were able to use the device for 60 min. The overall temperature reduction after 5 min of OC was 10.7°C (p < 0.01) and after 60 min 14.5°C (p < 0.01). The most common adverse events were bad fit of the mouthpiece (n = 6), hypersalivation (n = 6), and difficulties swallowing (n = 5). The oral device reduced the temperature of the oral mucosa as much as treatment with ice with tolerable adverse events. The mouthpiece will be remodeled to improve tolerability before further studies are conducted.

Enhancing Energy Saving in Air Cooling Devices by Intensifying External Heat Transfer

The aerodynamic processes of heated air in the ventilation shaft installed above the heat transferring bundle of bimetallic finned tubes are studied. The regions of suppressed natural, steady, and unsteady mixed air convection in the bundle depending on the degree of narrowing of the outlet section of the ventilation shaft are determined. The maximum Nusselt numbers for multi-row bundles and their corresponding optimum parameters of the degree of narrowing of the outlet section of the ventilation shaft are determined. A method is proposed for determining the Reynolds numbers and the average air velocity during free convection for contracted smooth and finned tube bundles, which will allow optimization of heat transfer processes. The practical effectiveness of single- and two-row bimetallic finned tube bundles with a finning factor φ = 21 and an intertube spacing of 58 mm in air cooling and similar aircooled heat exchangers having a ventilation shaft is scientifically proved.

Experimental Investigation of Thermal and Hydraulic Characteristics of Finned Flat Tubes of the Oil Air Cooling Device

Air cooling devices are heat exchange units that are widely used in practice. However, they have a number of disadvantages due to the low value of the heat transfer coefficient from the air and the high resistance of finned tube bundles, which leads to large dimensions and the metal content of the device itself, to the need to develop a high power ventilator drive, but also to the need to demonstrate reduced energy efficiency. The objective of the present work is to determine optimal geometric sizes of finned flat heat exchange tubes manufactured by the techniques of extrusion and deforming cutting that reduce the weight and size characteristics of the heat exchange section of air cooling devices. The experimental studies of seven various samples of heat exchange sections, being different in fin pitch and height, tube section width, flat tube height and a number of inner channels, have determined the performance of each section with the use of the following criteria: thermal power, thermal efficiency, specific thermal heat transfer resistance, M. V. Kirpichev and V. M. Antuf’ev’s criteria. The obtained experimental data and the analysis of the passive method of enhancement in the near-wall area of the heat transfer surface finned by deforming cutting has shown that sample No 5 has maximum value of the performance criteria when the maximum height of a fin is 0.008 m and the minimum pitch of a fin is 0.0025 m over the investigated sample range. Thus, when the sizes of an oil air cooling device are maintained by using the amended heat transfer section of sample No 5, the amount of removed heat can be increased or the mass and dimensions of the device can be decreased while maintaining thermal power and, as a result, the power consumption for pumping can be decreased and the thermal-hydraulic performance of the device as a whole can be increased.

Исследование процесса воздушно-водоиспарительного охлаждения в аппаратах воздушного охлаждения

Исследование процесса воздушно-водоиспарительного охлаждения в аппаратах воздушного охлаждения

Design of Low-carbon and Environmentally-friendly Intelligent Air Ventilation and Cooling Device

Design of Low-carbon and Environmentally-friendly Intelligent Air Ventilation and Cooling Device

Experimental Study of Heat Exchange and Aerodynamic and Thermal Contact Resistance of Staggered Bundles of Tubes with Spiral Rolled Fins of Air-Cooled Devices

Results of a study of the thermal and dynamic characteristics of three types of six-row checkerboard bundles in a transverse flow in the interval of Reynolds number Re = (3−18) × 103 are presented. The experimental data are generalized by similarity equations. The heat-exchange coefficients of each transverse row of the bundle are measured and features that arise in the variation of heat exchange by row of the bundle are identified. The mean value of the thermal contact resistance in the range of variation of the temperature of the contact surfaces 79−95°С is found to be equal to 2.13·10− 4 m2·K/W. On the basis of results of the study it is shown that the use of an equilateral configuration of tubes in bundles should be rejected and replaced by an isosceles configuration with steps S1 = 68−69 mm and S2 = 55.4 mm, a configuration that is advantageous in terms of energy and on the basis of a cost-benefit analysis.

Beam quality analysis and optimization for 10 kW-level spectral beam combination system

Filter-based spectral beam combining provides a promising approach for power scaling and brightness enhancement, especially for broad-linewidth fiber lasers. In this paper, we have demonstrated the beam combining experiments of two high power broad-linewidth fiber lasers using an edge filter as the combining element and achieved 10.25 kW combined power with an efficiency of 97%. Due to the thermal lens effect, the combined beam quality shows obvious signs of deterioration, which occurs in all cases of high power spectral beam combination system, including grating-based and prism-based schemes. The surface deformation and the thermal behavior are monitored in real-time so as to research the mechanism of the combined beam quality deterioration during the combining process. The primary reason for the decline of beam quality could be attributed to the thermal induced change in the refractive index, which not only results in an inhomogeneous wave-front aberration but causes the different focal waists of the incident channels. To counterbalance these aberrations, an air-cooling device and a passively thermally compensated optical system based on CaF2 windows are integrated into the system. In this case, the thermal lensing effect is minimized and the beam quality deterioration factor (BQD) of the combined output beam has been improved 52% in horizontal direction and 101% in vertical direction, showing the great potential of the filter-based approach to achieve a combined beam with high power and excellent beam quality.

Thermal Management of Hybrid Energy Storage for Electromagnetic Launch

Hybrid energy storage device for electromagnetic launch has the characteristics of high energy density and high power density. The device will release a lot of heat in both charging and discharging processes, which will have a direct impact on the stability of the whole system. Through the analysis of the structural feature and the principle of discharging, this paper compares the effect of air-cooling and water-cooling method for the high temperature rise problem in the process of repeated large rate discharging. In order to effectively reduce the temperature and evaluate the thermal management effect, an experimental platform for electromagnetic launch is built. This paper takes kilovolt level discharging and charging experiments on the platform with air-cooling devices, and the temperature rise is within the upper limit. The simulation analysis of the two kinds of cooling methods during discharging process is taken. And the experiment and simulation result can ensure the safe and continuous operation of electromagnetic launch, with practical engineering significance.

Decision working medium for lower cycle CCGT trinary type

The object of the study are low-boiling substances, which can be used as working fluid in the Organic Rankine cycle (ORC) combine cycle gas turbine (CCGT) trinary type. Purpose of research is search for substances with the best thermodynamic, thermophysical and ecological properties. The calculation algorithm represents a mathematical calculation of CCGT in which the lower cycle, operating on low-boiling fluid and utilizes low-potential heat, as an air-cooling device On the basis of available scientific and practical facts on the use of working fluids the organic Rankine cycle for analysis were selected ozone-safe refrigerant: butane, pentane, R236ea, R236fa, R123, R245ca, R245fa, R365mfc, RC318. For these substances were found and tabulated critical pressure and temperature, condensation pressure, density and dynamic viscosity at a given condensation temperature. Studies have shown that the highest thermal net efficiency is achieved when using natural Freon pentane and synthetic R365mfc. Net efficiency CCGT strongly depends on the condensation temperature of the substance. For example, when using pentane when the condensation temperature decreases on 10 °C. net efficiency increases about 0.71 %.