Numerical solutions for laminar flow heat transfer and pressure drop in circular tubes for variable property fluids

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Effects of water quality and surface temperature on the scaling characteristics of cooling tower water

ENERGY AND EXERGY ANALYSIS OF DATA CENTER ECONOMIZER SYSTEMS By Michael E. Meakins Electrical consumption for data centers is on the rise as more and more of them are being built. Data center owners and operators are looking for methods to reduce energy consumption and electrical costs. One method of reducing facility costs for a chilled water plant is by adding an economizer. Most studies concerning economizer systems are conducted largely by looking at energy alone since the primary focus is reducing electrical costs. Understanding how much exergy is destroyed, where it is destroyed, and why it is destroyed provides a more complete view on how environmental impacts can be minimized while reducing energy usage. The purpose of this study is to develop energy and exergy-based models of the most common economizer systems. A normal chiller plant without an economizer and a chiller plant with an indirect wet-side economizer (the most common type of economizer system) are compared. Results show outdoor conditions influence facility energy consumption and exergy destruction. For a chiller plant operating with an economizer, the CRAH is found to be the largest source for exergy destruction. For a chiller plant without an economizer, the chiller is the largest source for exergy destruction.

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Energy and exergy analysis of data center economizer systems

Fouling problems of heat exchangers affect severely the performance of heat transfer process during the concentration of milk. In this investigation the strategy of anti-fouling is focused on investigate the optimal hydrodynamic flow. Two combined techniques, for resulting oscillating high values of shear stress on heat transfer surfaces, were applied in the current investigation. The two techniques are dissolved air flotation for microbubbles generation in the milk stream with pulsed flow for hydrodynamics conditions modifications. Four different applied air pressures of 0.1, 0.2, 0.3, and 0.6MPa for controlling the microbubbles discharge and three modes of pulsation were nominated as uniform pulsation, gradient pulsation and without pulsation. Plate heat exchanger used commonly in milk industry for thermal treatments. Commercial pilot scale of plate heat exchanger was operated at milk flow rate of 0.078 m3h-1 and heating level from 42 to 61°C. The results show that the application of air pressure for microbubbles generation and pulsation type have a significant effect on fouling layer prevention for more while 105 minutes (the experimented time). For these reasons, the use of the two integrated techniques can progress thermal process of the plate heat exchanger. The optimum treatment for fouling deterrence is at applied air pressure of 0.6MPa and gradient pulsation, frequency with 0.16Hz and two states of steadily, unsteady of 20 seconds and steady of 10 seconds, the fouling layer decreases by 76.5%, and the maximum value of the overall heat transfer coefficient obtained is 9688.4Wm-2K-1.

https://mjae.journals.ekb.eg/article_97619_767fe2436b9dc1dbfa3a5d847e1101b6.pdf

Bilal Ahmed Qureshi

Papers

Design, rating and exergy analysis of evaporative heat exchangers