Heat Exchanger Module Research Articles

Minimum Mass Polymer Seawater Heat Exchanger for LNG Applications

The present study explores the thermofluid characteristics of a corrosion-resistant, thermally enhanced polymer composite, seawater-methane heat exchanger module for use in the liquefaction of natural gas on offshore platforms. Several metrics, including the heat transfer rate, the mass-specific heat transfer rate, and the total coefficient of performance (COPT), are used to compare the thermal performance of polymer composites having a range of thermal conductivities with that of corrosion-resistant metals. For operating conditions considered typical of the natural gas liquefaction industry in the Persian Gulf, a 10 W/m K polymer composite is found to provide nearly identical heat transfer rate to that of a corrosion-resistant titanium heat exchanger, almost 50% higher mass-specific heat transfer than for titanium (at 200 W pumping power), and COPT values approximately twice that of a least-material titanium heat exchanger. The results contribute to establishing the viability of using polymer composites for gas-liquid heat exchanger applications involving seawater and other corrosive fluids.

Model for melt blockage (slug) relocation and physico-chemical interactions during core degradation under severe accident conditions

The model describing massive melt blockage (slug) relocation and physico-chemical interactions with steam and surrounding fuel rods of a bundle is developed on the base of the observations in the CORA tests. Mass exchange owing to slug oxidation and fuel rods dissolution is described by the previously developed 2D model for the molten pool oxidation. Heat fluxes in oxidising melt along with the oxidation heat effect at the melt relocation front are counterbalanced by the heat losses in the surrounding media and the fusion heat effect of the Zr claddings attacked by the melt. As a result, the slug relocation velocity is calculated from the heat flux matches at the melt propagation front (Stefan problem). A numerical module simulating the slug behaviour is developed by tight coupling of the heat and mass exchange modules. The new model demonstrates a reasonable capability to simulate the main features of the massive slug behaviour observed in the CORA-W1 test.

Means of improving the operating efficiency of air condensers at the Verkhne-Mutnovskaya Geothermal Power Plant in Kamchatka

Operation of the Verkhne-Mutnovskaya Geothermal Power Plant (VMGPP) has revealed ineffective summer-time performance of air condensers (AC), which is caused by an insufficient heat reserve. Four alternate schemes are examined for improvement of the operational efficiency of the AC: replacement of the four-by five-tier heat-exchange modules; installation of high-output fans; a combination of the first two schemes; and, installation of additional sections in each power-generating set. Based on thermodynamic analysis that we have adapted for conditions at the VMGPP, it is established that the last alternate scheme is optimal, andwill have a payback period of six years, and a heat reserve of more than 40%, a figure approaching requirements now in force.

Transient response of multi-pass plate heat exchangers considering the effect of flow maldistribution

Present study depicts the transient response of multi-pass plate heat exchangers (PHEs) considering flow maldistribution from port to channels. Apart from the flow maldistribution, fluid axial dispersion is also considered to take care of the fluid backmixing and other deviations from plug flow. It is assumed that each multi-pass PHE is a combination of single-pass PHEs and in each heat exchanger the fluid is distributed non-uniformly amongst channels. The fluid velocity varies from channel to channel within each module of the heat exchanger so also the heat transfer coefficient. The solution techniques have been presented here for 1-2 pass and 2-2 pass arrangements. The first one is solved by analysing successive modules of the heat exchanger and the next one by iterating the responses between two heat exchanger modules. The solution for each module has been obtained analytically by using Laplace transform followed by numerical inversion from frequency domain. The results show the effect of flow maldistribution and its effect combined with the conventional heat exchanger parameters in the transient regime. It is observed that the transient characteristics such as response delay, asymptotic value and time constant are strongly dependent on the multi-pass flow arrangement, maldistribution and backmixing characterised by axial dispersion.

The modeling of a standalone solid-oxide fuel cell auxiliary power unit

In this research, a Simulink model of a standalone vehicular solid-oxide fuel cell (SOFC) auxiliary power unit (APU) is developed. The SOFC APU model consists of three major components: a controller model; a power electronics system model; and an SOFC plant model, including an SOFC stack module, two heat exchanger modules, and a combustor module. This paper discusses the development of the nonlinear dynamic models for the SOFC stacks, the heat exchangers and the combustors. When coupling with a controller model and a power electronic circuit model, the developed SOFC plant model is able to model the thermal dynamics and the electrochemical dynamics inside the SOFC APU components, as well as the transient responses to the electric loading changes. It has been shown that having such a model for the SOFC APU will help design engineers to adjust design parameters to optimize the performance. The modeling results of the SOFC APU heat-up stage and the output voltage response to a sudden load change are presented in this paper. The fuel flow regulation based on fuel utilization is also briefly discussed.

Thermal Analysis of High-Pressure Metal Hydride Tank for Automotive Application

ABSTRACTA new type of hydrogen storage tank has been developed for fuel cell vehicles FCHV. The tank design is based on the 35MPa high-pressure cylinder vessel and the heat exchanger module including hydrogen absorbing alloy with high dissociation pressure is integrated in it. To hydrogen absorbing alloy, for example, Ti-Cr-Mn alloy with AB2 laves phase is applied. Its effective hydrogen weight capacity is 1.9 wt% and reaction enthalpy is −2 kJ/molH2. To optimize the heat exchanger, thermal analyzing method was developed to predict the amount of hydrogen absorption or desorption. The simulation consists of heat and mass balance. Heat balance is made by the hydrogen absorbing alloy, heat exchanger and coolant each other. Also reaction heat of the hydrogen absorbing alloy and compressed heat are considered. The reaction heat is calculated from the equation of reaction rate that is derived experimentally.Furthermore, an additional simulation to predict the charging performance of on-board high-pressure MH tank system by the radiator cooling will be reported. With this simulation, it will become possible to make parameter studies to investigate how the operating conditions influence the performance of tank system.

High-pressure Metal Hydride Tank for Fuel Cell Vehicles

AbstractA new type of hydrogen-absorbing alloy tank has been developed. The high-pressure metal hydride (MH) tank has been designed based on a 35 MPa cylinder vessel. The heat exchanger module is integrated into the tank. Its advantage over high-pressure cylinder vessels is its large hydrogen storage capacity, for example 7.3 kg with a tank volume of 180 L. Cruising range is about 2.5 times longer than that of a 35 MPa cylinder vessel system with the same volume.The hydrogen-charging rate of this system is equal to the 35 MPa cylinders without any external cooling facility. Furthermore, release of hydrogen at 243 K is enabled due to the use of a hydrogen-absorbing alloy with a high disassociation pressure, Ti-Cr-Mn alloy with AB2 laves phase. It is thought that the high-pressure MH system is one realistic option for fuel cell vehicles to achieve a cruising range of over 700 km.

水素貯蔵材料を利用した車載水素貯蔵システムの研究高圧型水素吸蔵合金タンク

Although fuel cell vehicles have great potential as future vehicles, it is also realized that further breakthrough technologies to solve essential problems, such as cost and cruising range to be competitive with internal combustion engine vehicles. We have developed a new type of hydrogen-absorbing alloy tank. The high-pressure metal hydride (MH) tank is designed, based on the 35 MPa cylinder vessel. The heat-exchanger module including hydrogen-absorbing alloy is integrated in the tank. Its advantage over high-pressure cylinder vessel is large hydrogen storage capacity, for example, 7.3 kg at the 180 L tank volume. Cruising range is about 2.5 times longer than that of the same volume 35 MPa cylinder vessel system. While the conventional hydrogen-absorbing alloy tank has problems in charge and discharge process, the hydrogen charging rate of this system is equal to 35 MPa cylinder without external cooling facility. Furthermore, the hydrogen-absorbing alloy, Ti-Cr-Mn with AB2 laves phase can release hydrogen at 243 K. Its dissociation pressure at 243 K is 0.5 MPa. High-pressure MH system shows a realistic way to obtain adequate cruising range over 700 km. To develop a practical hydrogen tank for fuel cell vehicles, estimated target of hydrogen storage capacity of alloys is 3-4 mass% and 1600-2400 times as volumetric density.

Low-cost compact primary surface recuperator concept for microturbines

By the year 2000, microturbines in the 25–75 kW power range are projected to find acceptance in large quantities in the distributed power generation field, their major attributes include low emissions, multifuel capability, compact size, high reliability and low maintenance. For this type of small turbogenerator, an exhaust heat recovery recuperator is mandatory in order to realize a thermal efficiency of 30% or higher. The paramount requirements for the recuperator are low cost and high effectiveness. These characteristics must be accomplished with a heat exchanger that has good reliability, high performance potential, compact size, light weight, proven structural integrity, and adaptability to automated high volume production methods. In this paper, a recuperator concept is discussed that meets the demanding requirements for microturbines. The proposed stamped and folded metal foil primary surface recuperator concept has as its genesis, a prototype heat exchanger module that was fabricated as part of an energy research program in Germany over two decades ago. This novel heat exchanger approach was clearly ahead of its time, and lacking an application in the late 1970s was, alas, not pursued and commercialized. Based on this earlier work, a further evolution of the basic concept is proposed, with emphasis placed on the following: (1) minimization of the number of parts, (2) use of a continuous fabrication process, (3) matrix overall shape and envelope flexibility (annular or platular geometry), (4) ease of turbogenerator/recuperator integration, and (5) a later embodiment of a bi-metallic approach, towards the goal of establishing a compact and cost-effective recuperator for the new class of very small gas turbines that are close to entering service. For a representative microturbine, an annular recuperator would have only five basic parts. The matrix cartridge would be essentially a plug-in component, analogous to an automobile oil filter element. In this paper, the important role that the recuperator has on turbogenerator performance is discussed, together with a summary of the early prototype heat exchanger development. The major requirements, features and cost goals for a compact primary surface recuperator for microturbine service, are also covered.

99/01405 Condensing economizers for efficiency improvement and emissions control in industrial boilers : Butcher, T. A. et al. Combust. Can. 1996 Conf.: Future Changing Role Combust. Can. Effic. Environ., 1996, Paper7/1–7/15

Condensing economizers recover sensible and latent heat from boiler flue gas, leading to marked improvements in thermal efficiency. This paper summarizes the current commercial status and continuing development efforts with one type of condensing economizer. In this design Teflon{reg_sign} covered tubes and enclosure walls are used to handle the corrosive condensate. Flue gas flows around the tubes and feed water, being heated, flows through the inside. In addition to improving thermal efficiency, condensing economizers can also be used to reduce particulate emissions primarily by inertial impaction of particles on tube surfaces, water droplets, and added impactors. Collected particles are then removed with condensate. Water sprays directly on the tubes can be used to enhance particle capture. With coal-firing, tests have shown particle removal efficiencies as high as 98%. To enhance the emissions control potential of condensing economizer technology a two-stage economizer system concept has been developed. Two heat exchanger modules are used. The first is a downflow design and recovers primarily sensible heat from the flue gas. The second is upflow and recovers mostly latent heat. Condensate is collected in a transition plenum between the two stages. This configuration, termed the Integrated Flue Gas Treatment System, provides great flexibility for implementing emissions reduction strategies. Particulate emissions can be reduced without impacting sensible heat recovery by recirculating collected condensate to spray nozzles at the top of the second stage heat exchanger. In tests at BNL with heavy oil firing, particulate reductions over 90% and final emission rates on the order of.005 lb/MMBtu are achieved. Adding sorbents to the recirculated condensate reduces sulfur dioxide emissions and SO{sub 2} removal efficiencies over 95% are achieved. Also, condensing economizers show great potential for the removal of certain air toxics such as mercury and nickel.

Heat exchange in short microtubes and micro heat exchangers with low hydraulic losses

Miniaturization of heat exchangers opens up the way to a considerable increase of their volumetric characteristics. We examine the changes in heat transfer due to decreasing tube size and relative length. To get a higher overall thermal power, we have considered a “checkmate” design that allows to combine a number of micro cross-flow heat exchange modules. The requirement for low overall pumping power limits the pressure drop and also the minimal diameter of heat exchange tubes. An estimated volumetric heat transfer coefficient of a single symmetric air–air module of 50 mm3 volume (including supply channels) and 6 mm height is 4.3 MW/m3 K (at 260 Pa pressure drop, temperature difference of 5 K, pumping power comprising 4.3% of the thermal power, and micro tube size of 128×1200 μm). Micro machine-tools and assembly devices will allow fabrication of low-cost modules of this and smaller sizes and the ability to combine them into compact heat exchangers with high thermal power.

Cold Energy Generation Characteristics of Adsorption Heat Pump Using Direct Heat Exchange Module.

Heat and mass transfer characteristics in an adsorption heat pump (AHP) using a direct heat exchange module (DS-module) of silica gel were experimentally studied on the basis of results compared with those for the AHP with a multiple adsorbent-tube (MAT) type adsorber. Ultimate heat transfer enhancement for an adsorber of the AHP was almost achieved by using the DS-module and the possibility of its application to a refrigerator for producing low temperature cold heat energy was suggested.

Cold energy generation characteristics of an adsorption heat pump using a direct heat exchange module

Heat and mass transfer processes in an adsorption heat pump (AHP) using a direct heat exchange module (DS-module) of silica gel were experimentally studied and compared with those for an AHP with a multiple adsorbent tube (MAT) type adsorber. Ultimate heat transfer enhancement for an adsorber of the AHP was almost achieved by using the DS-module and the possibility of its application to a refrigerator for producing low-temperature cold heat energy was proposed. © 1997 Scripta Technica, Inc. Heat Trans. Jpn Res, 25(7): 460–465, 1997

Comparative Study of Five Blood Cardioplegia Systems

Five blood cardioplegia delivery systems (Gish Straight Shot, Sorin BCD Advanced, A vecor MYOtherm, Baxter-Bentley HE-30, and Baxter-Bentley HE-30 Gold) were evaluated with respect to ease of rapid priming, coefficient of heat exchange, pressure drop, bubble trap capacity, and priming volume. Each system was placed in a roller pump circuit consisting of source and collection reservoirs, cardioplegia solution, and pre-post system pressure and temperature monitoring sites. A trial was performed on four units of each brand by first priming the circuit with 0.9% NaCI at 200 ml/min. Bovine blood (hematocrit 22%) was then introduced simulating use during bypass. Pressure drops across the heat exchanger were measured at flows of 200, 300, and 400 ml/min and at temperatures of 37°, 19°, and 4°C. Coefficient of heat exchange was determined at 300 ml/min flow. Air was infused into the system to quantify the bubble trap capacity of the heat exchanger module. Priming volume of the entire system and of the heat exchanger module were determined by draining each into a graduated cylinder. The Sorin system had significantly less priming volume when compared to all others. The HE-30 units had significantly higher heat exchange coefficients compared to all other systems. Variability was noted in pressure drop at the highest flows and lowest temperatures.

An OTEC Pilot Plant Heat Engine

This paper summarizes the heat-engine system design for an ocean thermal energy conversion (OTEC) plant and its integration in the platform, and describes system components and their performance and construction requirements together with the computed overall cycle performance and operation. Ancillary equipment and platform arrangement and support requirements are discussed as to their effect on the platform design. The heat engine and platform design is based upon the JHU/Applied Physics Laboratory (APL) folded-tube, shell-less heat exchanger module concept as developed from analytical and experimental work previously reported. The heat engine design discussed is among the candidates for the construction of large commercial OTEC plantships. In the APL concept, the plantship will cruise (graze) the tropical oceans to utilize the maximum available ocean temperature difference. They will produce energy-intensive products such as ammonia, which can be synthesized from sea water and air and shipped to U.S. or foreign ports for use as fertilizer or as a hydrogen fuel carrier. The pilot plant design presented is for a 10–20-MW net output plant made up of 2.5-MWe net heat exchanger modules manifolded to 5 MWe net turbine-generator sets. In this approach, it is anticipated that all construction requirements, manifolding, cycle control, and installation and operational requirements can be determined and evaluated for the detailed design of large commercial vessels.

Requirements for structural ceramics in advanced power plants

During the last decade, considerable research and development has been carried out to demonstrate the use of structural ceramics, especially silicon carbide and silicon nitride, in high temperature gas turbines. A smaller but significant effort has been conducted to demonstrate the feasibility of ceramic heat exchangers. Design methods have been developed to take into account the brittle nature of ceramics. Thus, the viability of ceramic components in small turbines and subscale heat exchanger modules has been demonstrated for short test times. Use of ceramics in largescale advanced power plants will require considerable additional effort to ensure longterm durability and high reliability.

METHODOLOGY FOR ENERGY RECOVERY FROM LOWER TEMPERATURE EXHAUST AIRSTREAMS OF FOOD PLANTS

ABSTRACTA cross flow plate air to air heat exchanger module of simplified design was constructed to obtain cost and operating data. The fabrication of corrugated metal spacers was found to be a major cost. Therefore design criteria were developed for a simple “do‐it‐you” self” corrugation system. Extrapolation of prototype costs to full size installations shows that a payback of 6 months or less is possible for typical food plant installations.