Showing papers on "Heat exchanger published in 2011"

Process feed management for semiconductor substrate processing

Abstract: Embodiments related to managing the process feed conditions for a semiconductor process module are provided. In one example, a gas channel plate for a semiconductor process module is provided. The example gas channel plate includes a heat exchange surface including a plurality of heat exchange structures separated from one another by intervening gaps. The example gas channel plate also includes a heat exchange fluid director plate support surface for supporting a heat exchange fluid director plate above the plurality of heat exchange structures so that at least a portion of the plurality of heat exchange structures are spaced from the heat exchange fluid director plate.

Geotechnical Analysis of Heat Exchanger Piles

Abstract: There is currently a lack of established calculation method for the geotechnical design of heat exchanger piles, although the technology is experiencing a fast expansion. Instead of quantifying the effects of temperature changes on the static behavior of heat exchanger piles, the common geotechnical practice is to apply a large overall security factor. This is done in order to be on the side of safety with respect to thermal effects. The few existing in situ experiments show that applying a thermal load induces a significant change in the stress-strain state of a pile. This paper presents a geotechnical numerical analysis method, based on the load transfer approach, which assesses the main effects of temperature changes on pile behavior. The method is validated on the basis of two in situ measurements of the loads and deformations experienced by heat exchanger test piles. The occurrence of critical design situations is further discussed. Some conclusions are formulated on concrete failure and the full mobilization of the pile shaft friction and base resistance during the operation of the heat exchange system.

Refrigerant injection for heat pumping/air conditioning systems: Literature review and challenges discussions

Abstract: This paper reviews the major research on refrigerant injection techniques in detail. Liquid and vapor refrigerant injection techniques are discussed and compared. The current research on refrigerant injection techniques falls into two categories: system level research and component level research. The system level research is focused on low ambient temperature heating, heat pump water heating, high ambient temperature cooling, cycle comparison, and control strategy development. Internal heat exchanger and flash tank cycles are the two typical cycles for refrigerant injection. These two cycles are discussed and compared in detail. The component level research is focused on employing different types of compressors, variable speed compressors, the injection process, and the flash tank. Different types of compressors employing refrigerant injection are presented. Based on the literature study, the potential future research directions are presented and discussed. The flash tank cycle control strategy and refrigerant charge management strategy are worth further research efforts. Compressor design can be improved in order to optimize the performance with refrigerant injection. The appropriate design of flash tanks plays a vital role in achieving appropriate two-phase flow patterns in the flash tank. Computational Fluid Dynamics (CFD) modeling can be a useful tool to facilitate the design of the flash tank.

An Analytical Method to Calculate Borehole Fluid Temperatures for Time-scales from Minutes to Decades

Abstract: Knowledge of borehole exit fluid temperature is required to optimize the design and performance of ground source heat pump systems. The borehole exit fluid temperature depends upon the prescribed heat injection and extraction rates. This paper presents a method to determine the fluid temperature of a single or a multiple borehole heat exchanger for any prescribed heat injection or extraction rate. The fluid temperature, from minutes to decades, is determined using step response functions. An analytical radial solution is used for shorter times. A finite line-source solution is used for longer times. The line-source response function has been reduced to one integral only. The derivative, the weighting function, is given by an explicit formula both for single boreholes and any configuration of vertical boreholes.

A review on microchannel heat exchangers and potential applications

Abstract: Energy conversion and utilization are continuous but ever increasing processes for sustainability and economic development. Environmental concerns, such as thermal and air pollution, have dictated the practices of energy conservation and recovery, as well as the implementation of clean energy sources. Heat exchangers are an important component for processes where energy conservation is achieved through enhanced heat transfer. Such issues as increased energy demands, space limitations, and materials savings have highlighted the necessity for miniaturized light-weight heat exchangers, which provide high heat transfer for a given heat duty. However, while traditional heat exchangers employ conventional tubes (⩾6 mm) with various cross-sections, orientations, and even the enhanced surface textures, the technology is nearing its limits. Microchannels (broadly ⩽1 mm) represent the next step in heat exchanger development. They are a particular target of research due to their higher heat transfer and reduced weight as well as their space, energy, and materials savings potential over regular tube counterparts. In contrast to traditional tube heat exchangers, the heat transfer and fluid flow correlations, and the systematic design procedures are not yet well established for microchannels. It remains to be established whether the classical fluid flow and heat transfer theories and correlations are valid for microchannels. Numerous investigations are underway with researchers consolidating evidence on both sides of this question. This paper surveys the published literature on the status and potential of microchannels, and it identifies research needs, and defines the scope for long-term research. Based on results from the review, an air-to-liquid crossflow experimental infrastructure has been developed and commissioned. It will be used to investigate the heat transfer and fluid flow for a variety of working fluids in different microchannel test specimens. Further information and the heat balance status of the developed test facility are also presented. Copyright © 2010 John Wiley & Sons, Ltd.

Heat Exchanger Fouling: Mitigation and Cleaning Strategies

Abstract: Heat exchangers are the workhorse of most chemical, petrochemical, food-processing, and power-generating processes. The global heat exchanger market is estimated to top a total of $12.7 billion by ...

A review on the experimental and analytical analysis of earth to air heat exchanger (EAHE) systems in Turkey

Abstract: During the last three decades, a number of studies have been conducted by various investigators in the design, modeling and testing of earth to air heat exchanger (EAHE) systems. This paper reviews the studies conducted on the experimental and analytical analysis of EAHE systems in Turkey and around the world as of the end February 2011. The studies undertaken on the EAHE systems are categorized into two groups as follows: (i) open loop for space heating/cooling and (ii) closed loop for space heating/cooling systems. This paper investigates the studies on EAHEs, also known underground air tunnel systems.

Experimental investigation on the effect of mixing length on the performance of two-phase ejector for CO2 refrigeration cycle with and without heat exchanger

Abstract: In ejector system using the promising natural refrigerant CO 2 , the mixing of high-speed two-phase primary flow and suction vapor is crucial in designing an efficient ejector. In this study, the effect of mixing length on ejector system performance was analyzed experimentally. The mixing lengths used were 5 mm, 15 mm, and 25 mm, with constant rectangular cross-section. The experiments were performed for both ejector and conventional expansion systems with and without internal heat exchanger (IHX) at different operating conditions. Based on the experimental results, mixing length had significant effect on entrainment ratio and on magnitude and profile of pressure recovery. The 5 mm and 15 mm types yielded the lowest and highest ejector efficiency and COP in all of the conditions used in this research, respectively. The use of IHX had net positive effect on system performance which verified the results of our previous study. A COP improvement of up to 26% over conventional system was obtained but improper sizing of mixing length lowered the COP by as much as 10%.