Improved prediction of shell side heat transfer in horizontal evaporative shell and tube heat exchangers

This paper presents an improved prediction method for the heat transfer and pressure drop in the shell side of a horizontal shell and tube evaporator. The results from an experimental test program are used in which a wide range of evaporating two-phase shell side flow data was collected from a TEMA E-shell evaporator. The data are compared with shell side heat transfer coefficient and pressure drop models for homogeneous and stratified flow. The comparison suggests a deterioration in the heat transfer data at low mass fluxes consistent with a transition from homogeneous to stratified flow. The pressure drop data suggest a stratified flow across the full test range. A new model is presented that suggests the transition in the heat transfer data may be due to the extent of tube wetting in the upper tube bundle. The new model, which also takes into account the orientation of the shell side baffles, provides a vast improvement on the predictions of a homogenous type model. The new model would enable designers of shell side evaporators/reboilers to avoid operating conditions where poor heat transfer could be expected, and it would also enable changes in process conditions to be assessed for their implications on likely heat transfer performance. (Abstract from WOK

Using a side-branched volume to tune the acoustic field in a looped-tube travelling-wave thermoacoustic engine with a RC load

Travelling-wave thermoacoustic engine utilises a compact acoustic network to obtain a right time-phasing between the acoustic velocity and pressure oscillations within the regenerator to force gas parcels to experience a Stirling-like thermodynamic cycle. As such, thermal energy can be converted to mechanical work (i.e., high-intensity pressure waves). It is therefore crucial to control the time-phasing carefully to improve the performance of thermoacoustic engines. Various ways have been proposed and demonstrated for adjusting time-phasing, including both passive and active methods. The aim of this study is to introduce a new passive phase tuning method (i.e., a side-branched acoustic volume) to tune the time-phasing within a looped-tube travelling wave thermoacoustic engine. The proposed concept has been investigated both numerically and experimentally in this research. An experimental rig was simulated and designed using DeltaEC software (Design Environment for Low-amplitude ThermoAcoustic Energy Conversion). It was then constructed according to the obtained theoretical model. The result of this study showed a qualitative agreement between experimental measurement and numerical simulations, demonstrating that the proposed technique can effectively adjust the phase angle between the acoustic velocity and pressure oscillations within the loop-tube thermoacoustic engines, and improve its performance

Optimizing of metal foam design for the use as a heat exchanger

The work deals with possibilities of using this specific material. It is focused on cast metal foams with a regular arrangement of internal cells and it refers to already used casting technologies - the production of metal foamswith the aid of sand cores. Metal foamsare used in many industries, such as: automotive, aerospace, construction, power engineering. They have unique propertiesand due to lower weight with sufficient strength and greater contact surface can be used, for example, for the conduction of heat. This article deals with the useof the metal foam as a heat exchanger. The efficiency of the heat exchanger depends on its shape and size and therefore the study is focused first on the optimization of the shape before the proper manufacture.Web of Science6341881187

A review of metal foam and metal matrix composites for heat exchangers and heat Sinks

Recent advances in manufacturing methods open the possibility for broader use of metal foams and metal matrix composites (MMCs) for heat exchangers, and these materials can have tailored material properties. Metal foams in particular combine a number of interesting properties from a heat exchanger's point of view. In this paper, the material properties of metal foams and MMCs are surveyed, and the current state of the art is reviewed for heat exchanger applications. Four different applications are considered: liquid-liquid, liquid-gas, and gas-gas heat exchangers and heat sinks. Manufacturing and implementation issues are identified and discussed, and it is concluded that these materials hold promise both for heat exchangers and heat sinks, but that some key issues still need to be solved before broad-scale application is possible

Microwave apparatus for gravitational waves observation

In this report the theoretical and experimental activities for the development of superconducting microwave cavities for the detection of gravitational waves are presented.Comment: 42 pages, 28 figure

Plate frame and bar plate evaporator model validation and volume minimization

2019 Fall.Includes bibliographical references.Vapor compression chillers are the primary cooling technology for large building applications. Chillers have a large up front capital cost, with the heat exchangers accounting for the majority of the cost. Heat exchanger cost is a function of size, and therefore, a reduction in heat exchanger size can be correlated to a reduction in chiller capital cost. Few investigations focus on the reduction in heat exchanger size for vapor compression systems. Therefore, this investigation aims to decrease the size of chillers by predicting the minimum evaporator volume for a fixed performance. Only the evaporator was minimized because it was assumed that a similar process could be performed for the condenser in a future study. The study focused on a simple vapor compression cycle, and implemented high fidelity heat exchanger models for two compact heat exchanger types: brazed bar plate and gasketed plate and frame. These models accounted for variable fluid properties, phase change, and complex geometries within the evaporator core. The models used in this investigation were developed based on liquid-coupled evaporators in an experimental vapor compression system, and validated using collected data. The bar plate model was validated based on sizing and pressure drop to mean absolute errors of 14.2% and 14.0%, respectively. The plate frame model was validated for sizing to mean absolute errors equal to 7.9%; however, due to measurement uncertainty, pressure drop was not validated. The heat exchanger models were integrated into a simple vapor compression cycle model to determine the minimum required evaporator volume. Both heat exchanger types, in parallel and counter flow arrangements were minimized in this study. The minimum volume was achieved by varying the ratio between core length and number of channels. It was found that for both heat exchanger types, the parallel flow arrangement resulted in a smaller volume than the counter flow arrangement. Furthermore, the bar plate heat exchanger resulted in an optimum volume 91% smaller than the plate frame counterpart