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Heat Transfer and Heat Exchanger Principles
Published in Mary K. Theodore, Louis Theodore, Introduction to Environmental Management, 2021
Mary K. Theodore, Louis Theodore
Kern [1] defines heat-transfer equipment by the function it fulfills in a process. Heat exchangers recover heat between two process streams. In effect, they transfer thermal energy in the form of heat from one fluid to another. Kern [1] provides the following definitions for the various classes of heat exchangers. Heaters are used primarily to heat process fluids, and steam is usually employed for this purpose, although in oil refineries hot recirculated oil serves the same purpose. Coolers are employed to cool process fluids, water being the main cooling medium. Condensers are coolers whose primary purpose is the removal of latent instead of sensible heat. The purpose of reboilers is to supply the heat requirements of a distillation process as latent heat. Evaporators are employed for the concentration of a solution by the evaporation of water. If any other fluid is vaporized besides water, the unit is a vaporizer [1].
Environmental Considerations
Published in Martyn S. Ray, Martin G. Sneesby, Chemical Engineering Design Project, 2020
Martyn S. Ray, Martin G. Sneesby
Water is not part of the phthalic anhydride process and will not come into direct contact with any process stream in the system. Air coolers will be used to satisfy most of the process cooling requirements so that cooling water usage will be minimal. However, there will still be a cooling water link with the joint venture utilities plant that will service several local industries, and small amounts of PAN and other organic products could possibly enter the shared cooling-water system. Through economies of scale, the utilities plant is able to use the latest technology (e.g. automated dosing pumps, on-line analysers and advanced control applications) to remove contaminants and minimise emissions to the environment. The cooling-water circuit is a closed system and does not use either sea or river water, and it makes only small discharges of pH-neutral water to the environment. Biological fouling is controlled with phosphate additives rather than the more environmentally hazardous Chromate additives.
Lubrication Systems
Published in Peter Lynwander, Gear Drive Systems, 2019
The two types of coolers used are liquid to liquid or liquid to air. Figure 5.10 schematically illustrates an oil-water cooler. The hot oil entering through the shell side encounters the cooling water and an equilibrium of temperatures occurs, cooling the oil and heating the water. Where water is not available, radiators are used, blowing cooling air over oil tubes. Air-to-oil coolers require larger envelopes than water-to-oil coolers. Also, on hot days, the air temperature will limit the amount of cooling a radiator can achieve.
A parametric study of subcooled flow boiling of Al2O3/water nanofluid using numerical simulation and artificial neural networks
Published in Nanoscale and Microscale Thermophysical Engineering, 2022
Hasan Alimoradi, Erfan Eskandari, Mahdi Pourbagian, Mehrzad Shams
Nanofluids contain nanoparticles suspended in conventional base fluids. Considering their great potential for heat dissipation, they are frequently used in cooling systems, such as air-conditioners and electronic components coolers [1, 2]. There are two main categories of heat transfer mechanisms using nanofluid flows in heated channels: convective heat transfer without the phase change process and convective boiling flow [3]. The utilization of nanofluid flow boiling, however, has attracted more attention due to its significant heat transfer capability, and many research studies have been conducted to explore this important phenomenon [4–6]. A large group of research studies have been devoted to the study of nanoparticles in fluid flow [7, 8], bio [9, 10], cryogenic studies [11, 12], solar cells [13], acoustic [14], polymer studies [15, 16], and porous media [17]. There are other studies in this regard [18, 19], but as the focus of the present study is on the boiling phenomenon, thus in the following the studies in this regard are presented.
Experimental Investigation of Solar based Liquid Desiccant Indirect Evaporative Cooling system
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Anita A. Nene, Solaisamy Ramachandran
The characterization experiments showed that it is feasible to dehumidify the air by 4 to 8% using CaCl2 system with 3 l/min flow rate, which is similar to past research works. In case flow rate is increased, higher de-humidification may be possible; however, this results into more carryover losses and hence such balance is necessary. Problem of carryover could be reduced by using micro-porous membrane, – demister pad – allowing only air to pass through the membrane. However, the mass transfer resistance is increased due to this membrane and hence needs balancing usage. SPAR also affects the temperature drop at the output air and it is feasible to get between 4 and 5°C drops at SPAR of 0.8. Water flow rate in PPHE influences the performance as higher amount of water reduces heat exchange area. Polymer plate heat exchanger appears to be alternative to metal heat exchangers giving similar efficiency and performance but much more lighter, inexpensive and longer life. At location such as Pune in India, this system can give satisfactory performance upto 35°C ambient and RH more than 40% because if the RH is less than 40%, then dehumidifier acts as humidifier. Such system can be utilized for personal cooling as well as for supplying cooler air to improve efficiency of further processes.
A review of desiccant evaporative cooling systems in hot and humid climates
Published in Advances in Building Energy Research, 2021
Ismanizam Abd Manaf, Faisal Durrani, Mahroo Eftekhari
Evaporative cooling (EC) is responsible for the chill feeling one gets when a breeze flows over the skin; the air evaporates the water on the skin surface with body heat providing the energy for evaporation. A simple example to illustrate direct evaporative cooling can be found with hung wet mats in the doors and windows. Wind blowing through the mats cooled the air. This was the original evaporative air-conditioning. The basic idea was continually refined through the centuries. Mechanical fans provided air movement in the sixteenth century, cooling towers with fans that blew water-cooled air appeared inside factories in the early nineteenth century, and swamp coolers in the twentieth century (http://www.wescorhvac.com/Evaporative cooling white paper.htm). Modern technology has dramatically increased the efficiency and effectiveness of direct evaporative cooling and has enabled development of four other types of evaporative cooling: indirect evaporative cooling, indirect/direct evaporative cooling, indirect/indirect evaporative cooling, and indirect/DX evaporative cooling. Some are categorized into multiple types of evaporative coolers such as direct contact, indirect contact or a combination of both coolers.