Transfer Performance (transfer + performance)

Distribution by Scientific Domains

Kinds of Transfer Performance

  • heat transfer performance


  • Selected Abstracts


    A study on video performance of multipoint-to-point video streaming with multiple description coding over ad hoc networks

    ELECTRICAL ENGINEERING IN JAPAN, Issue 4 2010
    Keisuke Utsu
    Abstract Supporting multimedia applications over wireless networks has become a very active research topic recently because video applications are forecast to receive high demand in future wireless networks, such as ad hoc networks. However, enabling video transmission over wireless ad hoc networks is more challenging than over other wireless networks due to node mobility, interference, and the absence of a supporting infrastructure. This paper addresses the problem of video transmission over ad hoc networks. We propose to combine Multiple Description Coding (MDC) with multiple source transport (Multipoint-to-Point transfer: MP2P) in order to maintain smooth video streaming over wireless ad hoc networks. In this paper, we describe a comprehensive simulation and test bed experiment designed to show the effect of the proposed MP2P video transfer with MDC for two description cases of video streaming over wireless ad hoc networks. The results show that the proposed mechanism successfully improves video transfer performance in terms of video packet reachability and throughput. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 43,50, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20999 [source]


    Dimensioning of data networks: a flow-level perspective

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2009
    Pasi Lassila
    Traditional network dimensioning formulations have applied the Erlang model where the connections reserve capacity in the network. Until recently, tractable stochastic network models where the connections share the capacity in the network did not exist. The latter are becoming increasingly important as they can be applied to characterise file transfers in current data networks (e.g. IP networks). In particular, they can be utilised for dimensioning of networks with respect to the file transfer performance. To this end, we consider a model where the traffic consists of elastic flows (i.e. file transfers). Flows arrive randomly and share the network resources resulting in stochastically varying transmission rates for flows. Our contribution is to develop efficient methods for capacity planning to meet the performance requirements expressed in terms of the average transmission rate of flows on a given route, i.e. the per-flow throughput. These methods are validated using ns2 simulations. We discuss also the effects of access rate limitations and how to combine the elastic traffic requirements with those of real-time traffic. Finally, we outline how the methods can be applied in wireless mesh networks. Our results enable a simple characterisation of the order-of-magnitude of the required capacities, which can be utilised as a first step in practical network planning and dimensioning. Copyright © 2008 John Wiley & Sons, Ltd. [source]


    Fluid flow and heat transfer characteristics of cone orifice jet (effects of cone angle)

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2009
    Mizuki Kito
    Abstract The use of a jet from an orifice nozzle with a saddle-backed-shape velocity profile and a contracted flow at the nozzle exit may improve the heat transfer characteristics on an impingement plate because of its larger centerline velocity. However, it requires more power to operate than a common nozzle because of its higher flow resistance. We therefore initially considered the use of a cone orifice nozzle to obtain better heat transfer performance as well as to decrease the flow resistance. We examined the effects of the cone angle , on the cone orifice free jet flow and heat transfer characteristics of the impinging jet. We compared two nozzles: a pipe nozzle and a quadrant nozzle. The first one provides a velocity profile of a fully developed turbulent pipe flow, and the second has a uniform velocity profile at the nozzle exit. We observed a significant enhancement of the heat transfer characteristics of the cone orifice jets at Re=1.5×104. Using the cone orifice impinging jets enhanced the heat transfer rates as compared to the quadrant jet, even when the jets were supplied with the same operational power as the pipe jet. For instance, a maximum enhancement up to approximately 22% at r/do,0.5 is observed for ,=15°. In addition, an increase of approximately 7% is attained as compared to when the pipe jet was used. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20243 [source]


    Convective heat transfer and pressure drop of annular tubes with three different internal longitudinal fins

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2008
    Lin Tian
    Abstract Pressure drop and heat transfer characteristics of air in three annular tubes with different internal longitudinal fins were investigated experimentally at uniform wall heat flux. The tested tubes have a double-pipe structure with the inner blocked tube as an insertion. Three different kinds of fins, plain rectangle fin, plain rectangle fin with periodical ridges and wave-like fin, were located peripherally in the annulus. The friction factor and Nusselt number can be corrected by a power-law correction in the Reynolds number range tested. It was found that the tube with periodical ridges on the plain fin or with wave-like fin could augment heat transfer; however, the pressure drop was increased simultaneously. In order to evaluate the comprehensive heat transfer characteristics of the tested tubes, two criteria for evaluating the comprehensive thermal performance of tested tubes were adopted. They are: 1) evaluating the comprehensive heat transfer performance under three conditions: identical mass flow, identical pumping power, and identical pressure drop; 2) the second law of thermodynamics, i.e., the entropy generation. According to the two different evaluating methods, it was found that the tube with wave-like fins provided the most excellent comprehensive heat transfer performance among the three tubes, especially when it was used under higher Reynolds number conditions. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(1): 29,40, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20186 [source]


    Experimental study on heat transfer enhancement in the vertical nature convection by using delta-winglet longitudinal vortex generators

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2006
    Taowang
    Abstract This paper focuses on the study of heat transfer enhancement in natural vertical convection by using delta-winglet longitudinal vortex generators. In the experimental range of Rayleigh numbers, the effect of attack angle, height, and width of the winglet of longitudinal vortex generator (LVG) on heat transfer performance was experimentally investigated. The results showed that there was an optimal attack angle and that the height and width can affect the heat transfer. In terms of array performance, it was shown that initial arrays could enhance the performance of later arrays. Moreover, the effects of LVG and low rectangular fins were compared. The results showed that the effect of LVGs was greater than that of low rectangular fins. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(6): 402,409, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20126 [source]


    Experimental study on heat transfer enhancement on natural convection in a vertical plate by using longitudinal vortex generators arranged in rows

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2006
    JingAn Long
    Abstract Longitudinal vortices are capable of producing beneficial effects in heat transfer enhancement. Experiments in natural convection heat transfer enhancement were done on a vertical flat heating plate using delta-winglet longitudinal vortex generators (LVGs) arranged in rows. In an experimental range of Rayleigh number, the height and width of the winglet of the longitudinal vortex generator (LVG), the array form of the longitudinal vortex generators on the heat transfer performance were experimentally investigated, and the best height of the winglet of the longitudinal vortex generator was obtained. The results showed the change of the array form of the longitudinal vortex generators could affect the heat transfer effect. Finally by arranging some longitudinal vortex generator arrays with the appropriate interval, the whole heat transfer effect of the interval could reach a prime value. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(5): 351,358, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20119 [source]


    Effect of the plate thermal resistance on the heat transfer performance of a corrugated thin plate heat exchanger

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2006
    Hiroshi Iwai
    Abstract Two-dimensional conjugate conduction/convection numerical simulations were carried out for flow and thermal fields in a unit model of a counter-flow-type corrugated thin plate heat exchanger core. The effects of the thermal resistance of the solid plate, namely the variation of the plate thickness and the difference of the plate material, on the heat exchanger performance were examined in the Reynolds number range of 100[source]


    Experimental research of pool boiling heat transfer in horizontal narrow spaces

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2004
    Enshen Long
    Abstract Much progress has been made in high-performance electronic chips, the miniaturization of electronic circuits and other compact systems recently, which brings about a great demand for developing efficient heat removal techniques to accommodate these high heat fluxes. With this objective in mind, experiments were carried out on five kinds of test elements with distilled water and ethanol as working liquids. The test elements used in these experiments consisted of five parallel discs with diameters varying from 5 mm to 40 mm. The experiments were performed with the discs oriented horizontally and uniform heat fluxes applied at the bottom surfaces. The influence of narrow spacing, space size, working liquid property, and heat flux on boiling heat transfer performance in narrow spaces has been investigated. Experimental results showed that the boiling heat transfer coefficient of a narrow space was 3 to 6 times higher than that of pool boiling when the narrow space size and heat flux combine adequately, but the critical heat flux was lower than that of pool boiling. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 307,315, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20017 [source]


    Micro-bubble emission boiling from horizontal and vertical surfaces to subcooled parallel flow water

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2003
    Satoshi Kumagai
    Abstract Heat removal of more than 10 MW/m2 in heat flux has been required in high-heat-generation equipment in nuclear fusion reactors. In some conditions of water subcooling and velocity, there appears an extraordinary high heat flux boiling in the transition boiling region. This boiling regime is called micro-bubble emission boiling (MEB) because many micro-bubbles are spouted from the heat transfer surface accompanying a huge sound. The study intent is to obtain heat transfer performance of MEB in horizontal and vertical heated surfaces to parallel flow of subcooled water, comparing with CHF of this system. Three types of MEB with different heat transfer performance and bubble behavior are observed according to the flow velocity and liquid subcooling. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(2): 130,140, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10077 [source]


    An experimental study on vapor condensation of wet flue gas in a plastic heat exchanger

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2001
    L. Jia
    Abstract An experimental system investigating condensation heat transfer of wet flue gas was set up, and the heat transfer performance of vapor-gas mixture with vapor condensation was discussed. The experimental results of laminar flow in a plastic longitudinal spiral plate heat exchanger were obtained and are in good agreement with the modified classical film model. It is shown that the plastic air preheater can avoid acid corrosion in the low-temperature field for the boiler using fuel containing sulfur and recover latent heat of the water vapor of the wet flue gas. Also some SO2 was scrubbed during the vapor condensing process in the heat exchanger. © 2001 Scripta Technica, Heat Trans Asian Res, 30(7): 571,580, 2001 [source]


    Simulations of flow through fluid/porous layers by a characteristic-based method on unstructured grids

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2001
    Baili Zhang
    Abstract An upwind characteristic-based finite volume method on unstructured grids is employed for numerical simulation of incompressible laminar flow and forced convection heat transfer in 2D channels containing simultaneously fluid layers and fluid-saturated porous layers. Hydrodynamic and heat transfer results are reported for two configurations: the first one is a backward-facing step channel with a porous block inserted behind the step, and the second one is a partially porous channel with discrete heat sources on the bottom wall. The effects of Darcy numbers on heat transfer augmentation and pressure loss were investigated for low Reynolds laminar flows. The results demonstrate the accuracy and robustness of the numerical scheme proposed, and suggest that partially porous insertion in a channel can significantly improve heat transfer performance with affordable pressure loss. Copyright © 2001 John Wiley & Sons, Ltd. [source]


    Thermal-fluid transport phenomena in an axially rotating flow passage with twin concentric orifices of different radii

    INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2006
    Shuichi Torii
    Abstract This paper investigates the thermal fluid-flow transport phenomena in an axially rotating passage in which twin concentric orifices of different radii are installed. Emphasis is placed on the effects of pipe rotation and orifice configuration on the flow and thermal fields, i.e. both the formation of vena contracta and the heat-transfer performance behind each orifice. The governing equations are discretized by means of a finite-difference technique and numerically solved for the distributions of velocity vector and fluid temperature subject to constant wall temperature and uniform inlet velocity and fluid temperature. It is found that: (i) for a laminar flow through twin concentric orifices in a pipe, axial pipe rotation causes the vena contracta in the orifice to stretch, resulting in an amplification of heat-transfer performance in the downstream region behind the rear orifice, (ii) simultaneously the heat transfer rate in the area between twin orifice is intensified by pipe rotation, (iii) the amplification of heat transfer performance is affected by the front and rear orifice heights. Results may find applications in automotive and rotating hydraulic transmission lines and in aircraft gas turbine engines. Copyright © 2005 John Wiley & Sons, Ltd. [source]


    A study on latent heat storage exchangers with the high-temperature phase-change material

    INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2001
    Qiao He
    Abstract This paper presents a theoretical analysis and an experimental test on a shell-and-tube latent heat storage exchanger. The heat exchanger is used to recover high-temperature waste heat from industrial furnaces and off-peak electricity. It can also be integrated into a renewable energy system as an energy storage component. A mathematical model describing the unsteady freezing problem coupled with forced convection is solved numerically to predict the performance of the heat exchanger. It provides the basis for an optimum design of the heat exchanger. The experimental study on the heat exchanger is carried out under various operating conditions. Effects of various parameters, such as the inlet temperature, the mass flow rate, the thickness of the phase-change material and the length of the pipes, on the heat transfer performance of the unit are discussed combined with theoretical prediction. The criterion for analyzing and evaluating the performance of heat exchanger is also proposed. Copyright © 2001 John Wiley & Sons, Ltd. [source]


    MODELING HEAT EFFICIENCY, FLOW AND SCALE-UP IN THE COROTATING DISC SCRAPED SURFACE HEAT EXCHANGER

    JOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2002
    ALAN FRIIS
    ABSTRACT A comparison of two different scale corotating disc scraped surface heat exchangers (CDHE) was performed experimentally. The findings were compared to predictions from a finite element model. We find that the model predicts well the flow pattern of the two CDHE's investigated. The heat transfer performance predicted by the model agrees well with experimental observations for the laboratory scale CDHE whereas the overall heat transfer in the scaled-up version was not in equally good agreement. The lack of the model to predict the heat transfer performance in scale-up leads us to identify the key dimensionless parameters relevant for scale-up. [source]


    Flow distribution and mass transfer in a parallel microchannel contactor integrated with constructal distributors

    AICHE JOURNAL, Issue 2 2010
    Jun Yue
    Abstract Flow distribution and mass transfer characteristics during CO2 -water flow through a parallel microchannel contactor integrated with two constructal distributors have been investigated numerically and experimentally. Each distributor comprises a dichotomic tree structure that feeds 16 microchannels with hydraulic diameters of 667 ,m. It was found that constructal distributors could ensure a nearly uniform gas,liquid distribution at high gas flow rates where the ideal flow pattern was slug-annular flow. Nevertheless, at small gas flow rates where the ideal flow pattern was slug flow, a significant flow maldistribution occurred primarily due to the lack of large pressure barrier inside each distributor, indicating that dynamic pressure fluctuation in parallel microchannels greatly disturbed an otherwise good flow distribution therein. It was further shown that the present parallel microchannel contactor could realize the desired mass transfer performance previously achieved in one single microchannel under relatively wide operational ranges due to the integration of constructal distributors. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


    Attention cueing as a means to enhance learning from an animation

    APPLIED COGNITIVE PSYCHOLOGY, Issue 6 2007
    Björn B. de Koning
    The question how animations should be designed so that learning is optimised, is still under discussion. Animations are often cognitively very demanding, resulting in decreased learning outcomes. In this study, we tried to prevent cognitive overload and foster learning by focusing the learners' attention to one element (i.e. process) of an animation using a cueing technique. Psychology students viewed an animation of the cardiovascular system and were subsequently given a comprehension test and a transfer test. One group studied the animation without a visual cue, while for another group a visual cue was added to the animation. Results indicated that cueing not only enhanced comprehension and transfer performance for cued information, but also for uncued information. It is concluded that cueing can be used as a technique to improve learning from an animation. Results are interpreted in terms of cognitive load theory (CLT). Copyright © 2007 John Wiley & Sons, Ltd. [source]


    Active/Exploratory Training Promotes Transfer Even in Learners with Low Motivation and Cognitive Ability

    APPLIED PSYCHOLOGY, Issue 1 2010
    Nina Keith
    Active training approaches encourage self-directed exploration, whereas guided training stresses direct instruction and external guidance during training. The present research investigated interactions of individual-difference variables,motivation and cognitive ability,and training approach on performance in tasks that are similar to training tasks (analogical transfer) and tasks that are novel and distinct from training tasks (adaptive transfer). In accordance with a resource allocation framework (Kanfer & Ackerman, 1989), we expected effects of individual differences on transfer performance to be reduced after active/exploratory training compared with guided training, because participants of exploratory training engage in the same kind of metacognitive processing during training and transfer. Consequently, attentional demands are reduced during transfer, whereas for participants of guided training the transfer situation imposes high attentional demands. Experiment 1 (N= 37) taught a word processing program and Experiment 2 (N= 110) taught a presentation program using either active/exploratory or guided training. Consistent with previous research, training methods were equally effective for analogical transfer but active/exploratory training led to better adaptive transfer. In addition, interaction hypotheses were supported. Contrary to common recommendations, results suggest that active/exploratory training is suitable for promoting transfer even in learners with relatively low motivation and ability. La formation active stimule la recherche personnelle tandis que la formation dirigée accentue la transmission de directives et de conseils. Cette étude porte sur les interactions de variables relevant de différences individuelles (la motivation et les aptitudes cognitives) avec le type de formation sur la performance dans des tâches similaires aux tâches apprises (transfert analogique) et dans des tâches qui sont différentes de celles apprises (transfert adaptatif). A partir d'un modèle d'allocation de ressources (Kanfer & Ackerman, 1989), on s'attendait à ce que l'action des différences individuelles sur la performance suite au transfert soit atténuée à la suite d'une formation centrée sur l'exploration active, en comparaison de la formation dirigée, cela parce que les stagiaires bénéficiant d'une formation active font appel à la même catégorie de processus métacognitifs lors de la formation et du transfert. Par conséquent, une moindre attention est nécessaire durant le transfert, tandis que pour les stagiaires soumis à la formation dirigée, la situation de transfert exige une forte attention. La première expérience (N = 37) portait sur l'apprentissage d'un logiciel de traitement de textes et la deuxième sur l'apprentissage d'un logiciel de préparation d'un exposé utilisant soit une formation active, soit une formation dirigée. En accord avec les recherches antérieures, ces méthodes de formation sont d'une efficacité analogue en ce qui concerne le transfert analogique; mais la formation active permet un meilleur transfert adaptatif. De plus, les hypothèses sur les interactions ont été confirmées. A l'encontre des recommandations habituelles, nos résultats montrent que la formation active est favorable au transfert même quand les stagiaires présentent des aptitudes et des motivations relativement faibles. [source]


    Simultaneous extraction and concentration of penicillin G by hollow fiber renewal liquid membrane

    BIOTECHNOLOGY PROGRESS, Issue 2 2009
    Zhongqi Ren
    Abstract In this article, hollow fiber renewal liquid membrane (HFRLM) technique was used for recovery of penicillin G from aqueous solution. The organic solution of 7 vol % di-n-octylamine (DOA) + 30 vol % iso-octanol + kerosene was used as liquid membrane phase, and Na2CO3 aqueous solution was used as stripping phase. Experiments were performed as a function of carrier concentration in the organic phase, organic/aqueous volume ratio, pH, and initial penicillin G concentration in the feed phase, pH in the stripping phase, flow rates, etc. The results showed that the HFRLM process was stable and could carry out simultaneous extraction and concentration of penicillin G from aqueous solutions. As a carrier facilitated transport process, the addition of DOA in organic phase could greatly enhance the mass transfer rate; and there was a favorable organic/aqueous volume ratio of 1:20 to 1:30 for this system. The mass transfer flux and overall mass transfer coefficient increased with decreasing pH in the feed phase and increasing pH in the stripping phase, because of variation of the mass transfer driving force caused by pH gradient and distribution equilibrium. The flow rate of the shell side had significant influence on the mass transfer performance, whereas the effect of flow rate of lumen side on the mass transfer performance was slight because of the mass transfer intensification of renewal effect in the lumen side. The results indicated that the HFRLM process was a promising method for the recovery of penicillin G from aqueous solutions. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]


    Carbon Monoxide Mass Transfer for Syngas Fermentation in a Stirred Tank Reactor with Dual Impeller Configurations

    BIOTECHNOLOGY PROGRESS, Issue 3 2007
    Andrew J. Ungerman
    This study compares the power demand and gas-liquid volumetric mass transfer coefficient, kLa, in a stirred tank reactor (STR) (T = 0.211 m) using different impeller designs and schemes in a carbon monoxide-water system, which is applicable to synthesis gas (syngas) fermentation. Eleven different impeller schemes were tested over a range of operating conditions typically associated with the "after large cavity" region (ALC) of a Rushton-type turbine (D/T = 0.35). It is found that the dual Rushton-type impeller scheme exhibits the highest volumetric mass transfer rates for all operating conditions; however, it also displays the lowest mass transfer performance (defined as the volumetric mass transfer coefficient per unit power input) for all conditions due to its high power consumption. Dual impeller schemes with an axial flow impeller as the top impeller show improved mass transfer rates without dramatic increases in power draw. At high gas flow rates, dual impeller schemes with a lower concave impeller have kLa values similar to those of the Rushton-type dual impeller schemes but show improved mass transfer performance. It is believed that the mass transfer performance can be further enhanced for the bottom concave impeller schemes by operating at conditions beyond the ALC region defined for Rushton-type impellers because the concave impeller can handle higher gas flow rates prior to flooding. [source]


    CFD Study of Effects of Module Geometry on Forced Convection in a Channel with Non-Conducting Fins and Flow Pulsation

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2010
    B. O. Olayiwola
    Abstract CFD simulations were carried out to investigate the effects of the module geometry on forced convection in a rectangular channel containing series of regularly spaced non-conducting baffles with flow oscillation. The simulations were performed at constant wall temperature. Steady-flow Reynolds numbers Re in the range of 200 and 600 were studied. The results of the CFD simulations show that, for the effect fin spacing to be significant on heat transfer enhancement in finned system with oscillating flow, the oscillating flow velocity must be higher than the mean flow velocity. Superposition of oscillation yields increasing heat transfer performance with increasing fin height. Fin geometry with pyramidal shape yields highest performance in terms of the heat transfer effectiveness. [source]


    Enhancement Boiling Heat Transfer Study of a Newly Compact In-line Bundle Evaporator under Reduced Pressure Conditions

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2006
    Z.-H. Liu
    Abstract For common flooded-type evaporators, nucleate boiling heat transfer cannot occur on the heated tubes since heat fluxes and wall superheats of heated tubes are generally quite low. However, when the tube spacing is very small, nucleate boiling in restricted spaces can occur easily under low heat flux or low wall superheat conditions. The generation of nucleate boiling can effectively enhance the heat transfer performance of bundle evaporators. This study investigated experimentally the boiling heat transfer enhancement effects of the restricted space in compact in-line tube bundles with smooth tubes under various reduced pressures. The experimental results show that the compact in-line tube bundles have a significantly enhanced heat transfer compared to those of the common tube bundles, and there is an optimum tube spacing that provides the greatest heat transfer enhancement effect. The test pressures have a marked influence on the boiling heat transfer enhancement in the compact bundles. The heat transfer enhancement effect decreases with decreasing test pressure. In addition, the heat transfer enhancement effects of the in-line tube bundles are also compared with those of the staggered bundles. Under reduced pressure, there is no significant difference between the heat transfer enhancement effects for the two types of bundles. [source]