Tariq S. Khan

Review of Heat Transfer and Pressure Drop Correlations for Evaporation of Fluid Flow in Plate Heat Exchangers (RP-1352)

Plate heat exchangers have been widely used in dairy, food processing, paper/pulp, heating, ventilating, and other related industry. While single-phase flow in plate heat exchangers has been studied extensively, the industry lacks basic information on fluid flow evaporating in plate heat exchangers. This paper provides a review of heat transfer and pressure drop correlations for fluid flow evaporating in plate heat exchangers. Emphasis is placed on the application of a plate heat exchanger as an ammonia evaporator in a refrigeration system. It is shown via thorough research of related thermal–hydraulic phenomena that heat transfer and pressure drop correlations are needed for liquid ammonia flow evaporating in plate heat exchangers. The effects of plate geometry, plate material, oil/lubricant concentration, and several operating parameters on heat transfer coefficient and pressure drop for plate heat exchangers also need to be quantified.

Single-Phase Flow Pressure Drop Analysis in a Plate Heat Exchanger

Abstract Pressure drop characteristics of a gasketed commercial plate heat exchanger configured for single-phase water-to-water flow application are presented. Isothermal pressure drop data are provided for two symmetric 30°/30°, 60°/60° and a nonsymmetric 30°/60° (mixed) chevron plate configuration in the plate heat exchanger. Reynolds number was varied from 500 to 2,500. The experimental data are found to be a strong function of chevron angle and Reynolds number. Experimental results show that mixed plate configuration can be a choice in optimizing the plate heat exchanger design for improved performance. Based on experimental data, correlations are presented for estimation of friction factor.

A Computer Program for Working Fluid Selection of Low Temperature Organic Rankine Cycle

Fossil fuels are continuously depleting while the global energy demand is growing at a fast rate. Additionally, fossil fuels based power plants contribute to environmental pollution. Search for alternate energy resources and use of industrial waste heat for power production are attractive topics of interest these days. One way of enhancing power production and decreasing the environmental impact is by recuperating and utilizing low grade thermal energy. In recent years, research on use of organic Rankine cycle (ORC) has gained popularity as a promising technology for conversion of heat into useful work or electricity. Due to simple structure of ORC system, it can be easily integrated with any energy source like geothermal energy, solar energy and waste heat. A computer program has been developed in engineering equation solver (EES) environment that analyzes and selects appropriate working fluid for organic Rankine cycle design based on available heat sources. For a given heat source, the program compares energy and exergy performance of various working fluids. The program also includes recuperator performance analysis and compares its effectiveness on the overall thermal performance of the Rankine cycle. This program can assist in preliminary design of ORC with respect to best performing refrigerant fluid selection for the given low temperature heat source.Copyright

Recent Developments in Plate Exchangers—Ammonia/Carbon Dioxide Cascade Condensers

The use of carbon dioxide and ammonia in low temperature cascade systems is gaining momentum in the industrial refrigeration market. The use of a plate exchanger as cascade condenser is a viable option due to the high thermal efficiency and smaller footprint characteristics of such exchangers. There is a lack of reliable data in the open literature on condensation of carbon dioxide and evaporation of ammonia in such heat exchangers. This article presents the latest research on condensation of carbon dioxide and evaporation of ammonia in various corrugated plate exchangers at different saturation temperature and heat/mass flux. The data are reduced to generalized empirical correlations to be used as design tools by engineers. It also discusses the mechanical aspects of plate exchanges and their suitability in cascade systems.

A Review of Correlations for Outside Boiling of Ammonia on Single Tube and Bundles

ABSTRACT Shell and tube heat exchangers are widely used for various industrial refrigeration applications. This paper summarizes previous studies performed on single tube and bundles and the correlations thereof developed for ammonia. There are limited studies available on ammonia boiling outside single tube and bundle. The major driving force behind this paper is that an extensive work is currently underway on the subject of direct expansion of ammonia on the outside of a tube bundle by the authors. As of now, there are no such studies available in the open literature. In order to understand the process, it is important to follow up on previous studies on pool and convective boiling on single tubes and bundles with ammonia.

Experimental Investigation on Particle Deposition Patterns From Turbulent Pipe Flow

This paper reports an experimental study on sand particles deposition pattern in a horizontal circular pipe for several air flow rates and particle - air volumetric loading ratios. The experiments are conducted in a horizontal circular pipe with air - sand particles flow to simulate the solid particles movement in turbulent flow. A 50 mm diameter pipe was used in the current study while the averaged sand particles size used is around 100 μm. The particles are injected into the fully developed turbulent air flow. Digital cameras are used to capture the images of scaled test sections. The time dependent deposition layer properties including the geometry of deposition layers and the agglomeration pitch are studied. Hence, the average velocity of dune movement could also be calculated.The experimental results show that, in general, the deposition layer is continuous near the injection point, while small agglomerates are observed at the remote end. For the low air flow rate, striped-like dunes were found near injection point. For relatively higher air flow rates, the dunes became longer in size. Similarly, the length of agglomerates increased and the area fraction occupied by the agglomerates increased. Small aggregates are re-entrained from the frontal dunes of the deposition layer, and new agglomerates were gradually formed behind the next dune. The free flight length of solid particles for a range of air flow rates with different solid loading ratios was studied. It is found that for a given solid loading ratio, decreasing air velocity decreased the free-flight length of particles.Copyright