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Holger Martin

Bio: Holger Martin is an academic researcher from Karlsruhe Institute of Technology. The author has contributed to research in topics: Heat transfer & Plate heat exchanger. The author has an hindex of 24, co-authored 79 publications receiving 4061 citations. Previous affiliations of Holger Martin include Commonwealth Scientific and Industrial Research Organisation.


Papers
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Book ChapterDOI
TL;DR: In this article, the authors present a comprehensive survey emphasizing the engineering applications and empirical equations, presented for the prediction of heat and mass transfer coefficients within a large and technologically important range of variables.
Abstract: Publisher Summary Heating or cooling of large surface area products is often carried out in devices consisting of arrays of round or slot nozzles, through which air impinges vertically upon the product surface. This chapter presents a comprehensive survey emphasizing the engineering applications and empirical equations, presented for the prediction of heat and mass transfer coefficients within a large and technologically important range of variables. The local variations of the transfer coefficients are based on the experimental data for single round nozzles (SRN), arrays of round nozzles (ARN), single slot nozzles (SSN), and arrays of slot nozzles (ASN). The variation of local transfer coefficients is graphically represented. It also explores how to apply these equations in heat exchanger and dryer design as well as in optimization. The flow field of impinging flow is diagrammatically represented. External variables influencing heat and mass transfer in impinging flow depends on mass flow rate, kind and state of the gas and on the shape, size, and position of the nozzles relative to each other and to the solid surface. The design of high-performance arrays of nozzles is also discussed.

1,548 citations

Journal ArticleDOI
TL;DR: In this article, the generalized Leveque equation was used to predict the heat transfer coefficient of a plate and frame heat exchanger with chevron corrugation pattern, which is the most important design parameter with respect to fluid friction and heat transfer.
Abstract: Manufacturers of plate and frame heat exchangers nowadays mainly offer plates with chevron (or herringbone) corrugation patterns. The inclination angleof the crests and furrows of that sinusoidal pattern relative to the main flow direction has been shown to be the most important design parameter with respect to fluid friction and heat transfer. Two kinds of flow may exist in the gap between two plates (pressed together with the chevron pattern of the second plate turned into the opposite direction): the crossing flow of small substreams following the furrows of the first and the second plate, respectively, over the whole width of the corrugation pattern, dominating at lower inclination angles (lower pressure drop); and the wavy longitudinal flow between two vertical rows of contact points, prevailing at highangles (high pressure drop). The combined effects of the longer flow paths along the furrows, the crossing of the substreams, flow reversal at the edges of the chevron pattern, and the competition between crossing and longitudinal flow are taken into account to derive a relatively simple but physically reasonable equation for the friction factor ξ as a function of the angleand the Reynolds number Re. Heat-transfer coefficients are then obtained from a theoretical equation for developing thermal boundary layers in fully developed laminar or turbulent channel flow — the generalized Leveque equation — predicting heat-transfer coefficients as being proportional to (ξ·Re2)1/3. It is shown, by comparison, that this prediction is in good agreement with experimental observations quoted in the literature.

343 citations

Journal ArticleDOI
TL;DR: The voluminous literature available on thermal conductivities of packed beds without fluid flow is reviewed in this article, including experimental methods as well as theoretical approaches, and a classification of predictive models is attempted.
Abstract: The voluminous literature available on thermal conductivities of packed beds without fluid flow is reviewed. The discussion includes experimental methods as well as theoretical approaches. A classification of predictive models is attempted. One of these models is analysed in detail and recommended for practical use. The predictions of the model are compared with a large amount of experimental data. In the course of this comparison phenomena of physical interest and of technical significance are discussed. Most of the methods presented in this review retain validity for dispersed systems other than gas-filled packed beds and for properties other than the thermal conductivity.

259 citations

Journal ArticleDOI
TL;DR: For low Peclet numbers most of the experimentally obtained particle-to-fluid heat and mass transfer coefficients in packed beds were found to be some orders of magnitude below the values predicted for a single sphere in cross flow as mentioned in this paper.

255 citations

Journal ArticleDOI
TL;DR: In this article, an analytical study is made to calculate the axial velocity and pressure distributions in both the intake and exhaust conduits of plate heat exchangers, the flow distribution in the channels between the plates and the total pressure drop.

218 citations


Cited by
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Book
01 Jan 1984
TL;DR: In this paper, the authors describe a transition from Laminar boundary layer flow to Turbulent Boundary Layer flow with change of phase Mass Transfer Convection in Porous Media.
Abstract: Fundamental Principles Laminar Boundary Layer Flow Laminar Duct Flow External Natural Convection Internal Natural Convection Transition to Turbulence Turbulent Boundary Layer Flow Turbulent Duct Flow Free Turbulent Flows Convection with Change of Phase Mass Transfer Convection in Porous Media.

4,067 citations

Journal ArticleDOI
TL;DR: Fast pyrolysis for production of liquids has developed considerably since the first experiments in the late 1970s as mentioned in this paper, leading to significant advances in process development and a wide range of reactor configurations that have been developed to meet the stringent requirements for high yields of useful liquids, for use as a fuel in boilers, engines and turbines and as a source of chemical commodities.
Abstract: Fast pyrolysis for production of liquids has developed considerably since the first experiments in the late 1970s. Many reactors and processes have been investigated and developed to the point where fast pyrolysis is now an accepted feasible and viable route to renewable liquid fuels, chemicals and derived products. It is also now clear that liquid products offer significant advantages in storage and transport over gas and heat. These advantages have caused greater attention to be paid to fast pyrolysis, leading to significant advances in process development. The technology of fast pyrolysis for liquids is noteworthy for the wide range of reactor configurations that have been developed to meet the stringent requirements for high yields of useful liquids, for use as a fuel in boilers, engines and turbines and as a source of chemical commodities. This review summarizes the key features of fast pyrolysis and the resultant liquid product and describes the major reaction systems and processes that have been developed over the last 20 years.

1,686 citations

Book ChapterDOI
TL;DR: In this article, the authors present a comprehensive survey emphasizing the engineering applications and empirical equations, presented for the prediction of heat and mass transfer coefficients within a large and technologically important range of variables.
Abstract: Publisher Summary Heating or cooling of large surface area products is often carried out in devices consisting of arrays of round or slot nozzles, through which air impinges vertically upon the product surface. This chapter presents a comprehensive survey emphasizing the engineering applications and empirical equations, presented for the prediction of heat and mass transfer coefficients within a large and technologically important range of variables. The local variations of the transfer coefficients are based on the experimental data for single round nozzles (SRN), arrays of round nozzles (ARN), single slot nozzles (SSN), and arrays of slot nozzles (ASN). The variation of local transfer coefficients is graphically represented. It also explores how to apply these equations in heat exchanger and dryer design as well as in optimization. The flow field of impinging flow is diagrammatically represented. External variables influencing heat and mass transfer in impinging flow depends on mass flow rate, kind and state of the gas and on the shape, size, and position of the nozzles relative to each other and to the solid surface. The design of high-performance arrays of nozzles is also discussed.

1,548 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarize the knowledge of the production and properties of charcoal that has been accumulated over the past 38 millenia and summarize the potential of charcoal as a renewable fuel.
Abstract: In this review, we summarize the knowledge of the production and properties of charcoal that has been accumulated over the past 38 millenia. The manipulation of pressure, moisture content, and gas flow enables biomass carbonization with fixed-carbon yields that approachor attainthe theoretical limit after reaction times of a few tens of minutes. Much of the heat needed to carbonize the feed is released by vigorous, exothermic secondary reactions that reduce the formation of unwanted tars by augmenting the charcoal yield in a well-designed carbonizer. As a renewable fuel, charcoal has many attractive features: it contains virtually no sulfur or mercury and is low in nitrogen and ash; it is highly reactive yet easy to store and handle. Carbonized charcoal can be a good adsorbent with a large surface area and a semimetal with an electrical resistivity comparable to that of graphite. Recent advances in knowledge about the production and properties of charcoal presage its expanded use as a renewable fuel, red...

1,402 citations

Journal ArticleDOI
TL;DR: In this article, the authors derived a correlation for the Nusselt number of the form suggested by this evidence using a selection of the data and showed that this exponent should be a function of nozzle-to-plate spacing and of the radial displacement from the stagnation point.

1,030 citations