Cooling

ABSTRACT Thermal effects are critical factors on the performance and life of a Polymer Electrolyte Membrane (PEM) fuel cell system. Heat generation in a fuel cell stack is largely influenced by the exothermic electrochemical reactions at the cathode. Due to non-uniformity of reactions over the MEA area, heat generation and temperature distribution over the stack is also theoretically non-uniform. This work attempts to profile the thermal performance of an industrial PEM fuel cell stack. The stack power generation and cooling rates at the heat exchanger were monitored under specific working conditions. The discussion focused on causes of the temperature gradient, heat generation, cooling effectiveness, and the quality of the heat exchanger. The analysis demonstrates a significant relationship between stack temperature and generated power to the heat exchanger performance and coolant conditions.

Temperature and humidity control are crucial in next generation greenhouses. Plants require optimum temperature/humidity and vapor pressure deficit conditions inside the greenhouse for optimum yield. In this regard, an air-conditioning system could provide the required conditions in harsh climatic regions. In this study, the authors have summarized their published work on different desiccant and evaporative cooling options for greenhouse air-conditioning. The direct, indirect, and Maisotsenko cycle evaporative cooling systems, and multi-stage evaporative cooling systems have been summarized in this study. Different desiccant materials i.e., silica-gels, activated carbons (powder and fiber), polymer sorbents, and metal organic frameworks have also been summarized in this study along with different desiccant air-conditioning options. However, different high-performance zeolites and molecular sieves are extensively studied in literature. The authors conclude that solar operated desicca...

The temperature of the photovoltaic module has an adverse effect on the performance of photovoltaic modules. The photovoltaic module converts a small portion of energy from solar radiations into electricity while the remaining energy wastes in the form of heat. In this study, water cooled PV/T system was analyzed to enhance the efficiency by absorbing the heat generated by the photovoltaic modules and allowing the photovoltaic module to work at comparatively low temperature. For this system, four photovoltaic modules of two different types were used. To investigate the cooling effect, two modules were modified by making ducts at their back surface having inlet and outlet manifolds for water flow. The measurements were taken with cooling and without cooling of photovoltaic modules. The temperature was measured at inlet, outlet and at different points at the back of Photovoltaic modules. It was found that there was a linear trend between the module efficiency and temperature. The average module temperature of c-Si and p-Si modules without cooling was 13.6% and 7.2% lower respectively than the same modules without cooling. As a result of temperature drop, the average module electrical efficiency of c-Si and p-Si was 13% and 6.2% higher respectively compared to the modules without cooling. Flowing water also gains useful heat from PV module so the resultant overall energy of the system was much higher.

In this paper an analysis of energy use and energy conservation in the Malaysian rubber producing industries is presented. It has been found that rubber industries consume a substantial amount of energy. Excessive use of energy is usually associated with many industrial plants worldwide, and rubber plants are no exception. This study is based on the realization that enormous potential exists for cost-effective improvements in the existing energy-using equipment. Through the method of a walkthrough energy audit, power rating, operation time of energy-consuming equipment/machineries and power factor were collected. The data were then analyzed to investigate the breakdown of end-use equipment/machineries energy use. The results of the energy audit in the Malaysian rubber and rubber producing industries showed that the electric motor accounts for a major fraction of total energy consumption followed by pumps, heaters, cooling systems and lighting. Since the electric motor takes up a substantial amount of the total energy used in rubber industries, energy-savings strategies such as the use of high efficient motors, and variable speed drive (VSD) have been used to reduce energy consumption of motors used in rubber industries. Energy-savings strategies for compressed-air systems, boilers, and chillers have also been applied to estimate energy and cost savings. It has been found that significant amount of energy and; utility bills can be saved along with the reduction of emission by applying the foretold strategies for energy using machineries in the rubber industries.

http://www.sciencedirect.com/science/article/pii/S0306261909005558

Tháp giải nhiệt Tashin TSS & TSC được sản xuất hoàn toàn từ những chất liệu cao cấp không bị ăn mòn, độ bền cao, khả năng dẫn nhiệt tốt nên sử dụng tháp giả nhiệt Tashin TSS & TSC cho hiệu quả làm việc bền bỉ trong nhiều năm.
Điện máy Hoàng Liên hiện đang là đại lý phân phối chính hãng tháp nước giải nhiệt Tashin tại Hà Nội, TP.HCM và các tỉnh thành trên cả nước.
Truy cập: https://dienmayhoanglien.vn/thap-giai-nhiet-tss.html

Engine cooling system is crucial to maintain working temperature of vehicles' engine. The two main heat transfer fluids in typical cooling system are coolant and air. Under hood air flow when approaching radiator is highly non-uniform, thus 3D computational fluid dynamics is required to estimate air mass flow rates. While coolant circuit consists of numerous components, 1D thermal-fluid simulation is utilized to study temperature behavior of the coolant. Automotive designers should design a robust engine cooling system which is working well in both normal and severe driving conditions. When vehicles are keyed-off suddenly after some distance of driving, the coolant temperature tend to increase dramatically. This is because soaking heat at engine could not be transferred away timely, as water pump and cooling fan have stop working after keyed-off. In this study, transient coolant temperatures are observed closely with variety patterns of soaking heat. It is suggested to prolong operation of water pump and fan for a short while after keyed-off to reduce transient coolant temperature. © 2011 IEEE.

http://ieeexplore.ieee.org/ielx5/6118337/6118565/06119034.pdf?tp=&arnumber=6119034&isnumber=6118565

An overview is represented of the cryogenic technologies implementation in the heat treatment and deformation of metals. The areas are determined of most effective application of the cryogenic liquids and gases in the steel rolling production and heavy machines building with the aim of product quality improving, equipment and tools durability and reducing ecology impact on environment and working personnel.

For over 50 years, high-pressure gas turbine blades have been cooled using air bled from the compressor. This cooling results in very high rates of heat transfer, both within the fluid and within the blade, shown in figure 1. The heat transfer often occurs across large temperature differences and is thus highly irreversible. It is therefore surprising that little is understood about the effect of this heat transfer on turbine performance.

Lathe machines are used widely in all mechanical industries and workshops to carry out various operations on the mechanical parts. Turning, drilling, and cutting are very common operations performed on the mechanical parts. Mechanical part design needs precision of work as the dimensions of the part should be very accurate to fit in to the bigger machines. The main problem while working on lathe machine is the heat developed as the operations carried out are on the metallic parts. Due to continuous friction of the parts huge amount of heat is produces. Also the motors connected to the lathe undergoes huge load as there is huge requirement of torque. Hence the heat produced need to be addressed. We have designed a system for cooling for cooling of lathe machine. INTRODUCTION: Cooling is very important aspect of any machine. Lathe machines deals with the processing of mechanical parts. These parts are made up of metallic material and have good mechanical strength. The lathe machine is used to convert a piece of metal to the final part with considerations of dimensions and other mechanical properties. Heat produced in lathe machine is huge and it is produced in various parts of the machine. Lathe machine are used for performing the operations like turning, drilling, trimming and shaping the mechanical parts. These machines if cooled properly results in saving of money with improvement in the life of various parts. Authors have developed a unique system for cooling of lathe. The system is capable to cool multiple machines at a time. This machine found suitable for the mechanical workshops and the industries where there are multiple lathes working continuously to carry out production of various mechanical parts.

Cooling towers use the principle of evaporative cooling to remove process heat from the cooling water and reduces its temperature to the wet-bulb air temperature. It is a heat and mass transfer device. This method of cooling provides with efficient and environment-friendly method of cooling particularly in locations where sufficient cooling water cannot be easily obtained from natural sources or where concern for the environment imposes some limits on the temperature at which cooling water can be returned to the surrounding. Cooling towers are an important part of the nuclear power plants which remove heat from coolant (water) of the condenser and recirculate it. Natural draft cooling towers represent a relatively inexpensive and dependable means of removing heat from cooling water as air inside it is circulated by natural convection, no mechanical means such as fans propellers are needed. The performance of the natural draft cooling tower is dominated by wind speed, ambient air temperatures and humidity in the atmospheric conditions. This paper provides the analysis of designing a natural draft cooling tower considering all these parameters with the help of trial and iterative method. The effect of height, diameter, and the type of filling material selected, are studied.

With growing use of internet and exponential growth in amount of data to be stored and processed (known as ``big data''), the size of data centers has greatly increased. This, however, has resulted in significant increase in the power consumption of the data centers. For this reason, managing power consumption of data centers has become essential. In this paper, we highlight the need of achieving energy efficiency in data centers and survey several recent architectural techniques designed for power management of data centers. We also present a classification of these techniques based on their characteristics. This paper aims to provide insights into the techniques for improving energy efficiency of data centers and encourage the designers to invent novel solutions for managing the large power dissipation of data centers.

When dissolved in water, the crystalline powder saltpetre causes a chemical reaction that greatly reduces the temperature of the solution.  When a vessel containing a beverage is immersed in a basin of the cooled water, the effect spreads enough to chill the beverage.  This discovery was used in ancient Asia, and was adopted in Europe by the sixteenth century.  In my experiment, I wished to revive this technique and discover whether it could be applied practically in an SCA camp environment as a period method to chill beverages without the use of ice or modern refrigeration.  The results from the experiment proved that the technique is sound, and it does chill the basin and the beverage well.  However, it is sadly not cost effective or practical to use this method “in the field” unless an inexpensive and accessible source of industrial saltpetre can be found.

The purpose of carrying out this research work is to further amplify the advantages of implementing geothermal air conditioning system in Pakistan. The temperature of the soil at a certain depth remains consistent irrespective of the ambient temperature, the consistency in temperature of the soil all over the year provides a new way to the researchers, scholars, and scientists to work on the different techniques and methods of extracting the energy of ground for heating and cooling applications. To effectively utilize the natural source of energy (geothermal energy), a heat-exchange system has to be constructed. This is typically an arrangement of pipes with selected piping material and loop design, buried in the ground. Among many available circulating mediums, air and water are most widely used to harness energy from the ground in winter and vice versa in summer. A similar system has been proposed that can provide a sustainable solution for the alarming energy crisis in Pakistan. Soil temperature at a certain depth, adequate piping material, configuration and the coefficient of performance (COF) of the installed system evaluated experimentally. The temperature gradient of 23°C on average has been achieved from the developed working model.

The measured and forecasted changes in climate have an immediate influence on the planning of buildings and building services. The requirements toward the energy efficiency of buildings is increasing. Due to rising temperatures, the reduction of summer heat loads will become a dominant factor in the tempering of buildings.
Static and angle selective shading devices are an appropriate measure in the process of reducing summer gains and allowing the winter passive use of solar energy. They are independant of control mechanisms or user behaviour and are therefore more robust energetically and more predictable when dimensioning building services as opposed to moveable shading.
Static shading is an architectural medium. It dominates facades as an invariant graphic element and offers high design potential.
This thesis shows a basic formal typology of static shading devices and simple methods of valuating their influence on daylight, warmth and view. It concludes with a presentation and evaluation of tools for their exact dimensioning and their generation.

In this study, the performance of a prototype thermoelectric heating/cooling unit is investigated. In the
numerical analysis, temperature–pressure contours, and velocity vectors are obtained for the selected fin
geometry. In order to validate the numerical results, experimental analyses are carried out. The effects of
the air velocity on the temperature distribution of the fin surfaces and the variation of the psychrometric
properties of the air are measured for various TEC voltage differences. Thermal images are used to obtain
the temperature variation on fin surfaces. COP values for heating and cooling are calculated. For different
fan speeds, the heating and cooling COP values vary between 2.5 and 5, and 0.4 and 1, respectively. The
study shows that it is possible to use TECs as an alternative method for HVAC applications with properly
designed heat exchangers. Integrating them with photovoltaic panels provides utilization of solar energy,
especially in cooling applications.

Termodinamika sangat berharga untuk menganalisa sembarang sistem
yang melibatkan berbagai perpindahan energi; berbagai pemakaian
termodinamika yang praktis dan lazim dalam rekayasa adalah untuk
menganalisa berbagai sistem yang mengandung suatu zat kerja, biasanya
dalam fase cair atau gas, yang mengalir atau mendaur di dalam peralatan.
Dalam bab ini  berbagai karakteristik dari sejumlah sistem termodinamik akan
kita teliti, yang kebanyakan dari jenis yang baru disebutkan di atas dan
sebagai tambahan perilaku beberapa peralatan yang belum lazim tetapi
mempunyai prospek penggunaan praktis yang baik di masa depan akan kita
tinjau. Bebagai karakteristik ini dapat diprediksi dengan penggabungan
analisa termodinamika dengan pengalaman menjalankan perangkat keras.
Pada bagian lain akan ditinjau berbagai sistem yang cukup ideal sehingga
analisa performansinya masih tercakup oleh telaahan yang sudah dilakukan
hingga kini.
Berbagai sistem yang menjadi pusat perhatian disini adalah sistem
refrijerasi atau pendingin yang ingin dicapai untuk mempertahankan agar
suatu ruang tetap dingin dengan mengeluarkan energi sebagai panas secara
berkesinambungan dari ruang tersebut. Kebanyakan sistem tersebut
melibatkan suatu fluida kerja, seperti air atau udara, yang disirkulasikan
melalui sistem dalam suatu daur. Hukum kedua termodinamika menerapkan
berbagai batasan yang ketat terhadap performansi berbagai sistem
perpindahan termal dan perihal ini akan diteliti dalam berbagai uraian berikut.
Bidang temperatur entropi mempunyai peran yang penting; apabila zat
mengalami suatu proses reversibel, urut-urutan tingkat keadaan yang dilalui menggoreskan suatu garis (kurva) dalam bidang T-s. Karena proses
reversibel, perpindahan energi sebagai panas ke satu satuan massa zat
diwakili oleh luas di bawah kurva pada bidang T-s. Apabila zat mengalami
proses daur, tidak terdapat perubahan energi dalam netto untuk suatu daur,
jadi perpindahan energi netto ke satu satuan massa zat sebagai panas
selama daur berlangsung harus sama dengan perpindahan energi netto
sebagai kerja dari zat (kerja yang dilakukan), dan keduanya sama dengan
luas yang terkurung oleh lintasan reversibel dalam bidang T-s (Gambar 9.4).
Jadi, pernyataan proses T-s dapat digunakan sebagai perangkat grafik untuk
membandingkan dan menilai berbagai sistem termodinamik dan perangkat ini
akan digunakan secara ekstensif di dalam bab ini. Berbagai bidang
termodinamik lainnya juga sangat memperikan seperti nanti akan terlibat.

The effect of cooling methods after heat treatment on the microstructure and mechanical properties of reinforced high strength low alloy steel were studied. The microstructure characteristics were observed under OM (optical microscope), SEM (Scanning Electron Microscope). Charpy V Notch impact tests at different temperatures (-30°C, -10°C, 25°C) along with Tensile tests were performed and the mechanical properties were evaluated. The evaluated results indicated that cooling with water led to a mix of ferritic matrix and tempered martensite, whereas after air cooling the microstructure was a mix of ferritic matrix and tempered bainite. This is basically due to the intensity of cooling rate in both the cooling techniques. Ultimate tensile strength, yield strength, % elongation were compared for the different cooling techniques. In air cooling the combination of strength and toughness was better than in comparison with water cooling.

Single zone (SZ) air handling units (AHUs) are widely applied in the conditioned spaces. A SZ AHU typically consists of a chilled water cooling coil, a hot water heating coil, and a supply fan. For a constant volume (CV) SZ AHU or variable air volume (VAV) SZ AHU operating at a minimum airflow, the control valve of either the cooling coil or heating coil is modulated to vary the supply air temperature and consequently control space air temperature. Traditionally, a single control loop is applied to modulate the control valve directly based on the space air temperature. The traditional control is simplistic in nature, however, suffers significant drawbacks. Due to the thermal capacity of both the water in the coils and the air in the conditioned space, the system often becomes unstable due to nonlinear characteristics of the SZ AHU system and leads to hunting of the control valve. On the other hand, cascade control makes the control system more adaptive and robust. A cascade control can be applied to a SZ AHU in order to stabilize the system. The primary controller reads the room air temperature and determines the required supply air temperature for a secondary controller which then controls the heating/cooling coil valve. The purpose of this paper is to demonstrate the stability of the cascade control method in a SZ AHU system. A model of the SZ AHU system with transfer functions is developed for conventional and cascade control methods and root-locus analysis is performed. The results conclude that the cascade control improves the stability of the control valve by reducing the sensitivity to the change in the operating conditions.

This work describes the design and construction of a standing wave Thermoacoustically Driven Thermoacoustic Refrigerator (TADTAR). The thermoacoustic cooler is proposed in this study as an alternative sustainable solution to current issues with vapor compression refrigerators, due to its environmentally friendlier attributes and its solar energy driven capabilities. However, one of the main hindrances to the expansion of this technology is its current lack of efficiency and performance closely related to the designing of the device. Hence, a model has been designed and constructed to perform an experimental investigation of the device's performance at the University of Johannesburg. This model will mainly be used to investigate the dynamics of the TADTAR arrangement. The TADTAR consists of two thermoacoustic systems namely a thermoacoustic engine coupled to a thermoacoustic refrigerator. The thermoacoustic engine consists of a heat source and a cordierite honeycomb stack which converts heat into acoustic energy. The heat pumping takes place within a thermoacoustic refrigerator. Guidance on the material selection, constraints and calculation of the geometrical configuration describing the device constitute the main contribution of this work.

Wind catchers are natural ventilation systems based on the design of traditional architecture, intended to provide ventilation by manipulating pressure differentials around buildings induced by wind movement and temperature difference. Though the movement of air caused by the wind catcher will lead to a cooling sensation for occupants, the high air temperature in hot regions will result in little cooling to occupants. In order to maximise the properties of cooling by wind catchers, heat pipes were incorporated into the design. Computational Fluid Dynamics (CFD) was used to investigate the effect of the cooling devices on the performance of the wind catcher, highlighting the capabilities of the system to deliver the required fresh air rates and cool the ventilated space. Qualitative and quantitative wind tunnel measurements of the airflow through the wind catcher were compared with the CFD data and good correlation was observed. Preliminary field testing of the wind catcher was carried out to evaluate its thermal performance under real operating conditions. A cooling potential of up to 12˚C of supply air temperature was identified in this study.

Evaporative cooling system is a physical phenomenon in which the surrounding air cools an object or a liquid in contact with it. An extensive literature has been reviewed. The materials and methods used in the research involves, the two clay pots (bigger and smaller size), water, Okra, measuring devices (Thermometer and Hygrometer), and the wooden cover. A smaller pot was kept inside a bigger clay pot and the Inter-space was filled with riverbed sand which was made moist by adding water thrice a day i.e. morning, afternoon and evening. The result obtained showed that the okra can be stored for 14days in the mean temperature of (27.27, 32.92 and 29.68 O C) and relative humidity of (97.43, 47.08 and 66.30 %). Conclusively, the pot in pot evaporative cooler could be used in New Bussa, Nigeria during the dry season when the temperature is high and relative humidity is low.