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  • Open Access

    ARTICLE

    Flow Patterns and Heat Transfer Characteristics of a Polymer Pulsating Heat Pipe Filled with Hydrofluoroether

    Nobuhito Nagasato1, Zhengyuan Pei1, Yasushi Koito2,*

    Frontiers in Heat and Mass Transfer, Vol.22, No.1, pp. 49-63, 2024, DOI:10.32604/fhmt.2024.047502

    Abstract Visualization experiments were conducted to clarify the operational characteristics of a polymer pulsating heat pipe (PHP). Hydrofluoroether (HFE)-7100 was used as a working fluid, and its filling ratio was 50% of the entire PHP channel. A semi-transparent PHP was fabricated using a transparent polycarbonate sheet and a plastic 3D printer, and the movements of liquid slugs and vapor plugs of the working fluid were captured with a high-speed camera. The video images were then analyzed to obtain the flow patterns in the PHP. The heat transfer characteristics of the PHP were discussed based on the flow patterns and temperature distributions… More >

  • Open Access

    ARTICLE

    BIO-HEAT TRANSFER SIMULATION OF SQUARE AND CIRCULAR ARRAY OF RETINAL LASER IRRADIATION

    Arunn Narasimhan*, Kaushal Kumar Jha

    Frontiers in Heat and Mass Transfer, Vol.2, No.3, pp. 1-8, 2011, DOI:10.5098/hmt.v2.3.3005

    Abstract Pan Retinal photocoagulation (PRP), a retinal laser surgical process, is simulated using a three-dimensional bio-heat transfer numerical model. Spots of two different type of array, square array of 3 × 3 spots and a circular array of six spots surrounding a central spot, are sequentially irradiated. Pennes bio-heat transfer model is used as the governing equation. Finite volume method is applied to find the temperature distribution due to laser irradiation inside the human eye. Each spot is heated for 100 ms and subsequently cooled for 100 ms with an initial laser power of 0.2 W. Based on the outcome of… More >

  • Open Access

    ARTICLE

    Experimental Evaluation of Individual Hotspots of a Multicore Microprocessor Using Pulsating Heat Sources

    Rodrigo Vidonscky Pinto1, Flávio Augusto Sanzovo Fiorelli2,*

    Frontiers in Heat and Mass Transfer, Vol.21, pp. 427-443, 2023, DOI:10.32604/fhmt.2023.041917

    Abstract The present work provides an experimental and numerical procedure to obtain the geometrical position of the hotspots of a microprocessor using the thermal images obtained from the transient thermal response of this processor subject to pulsating stress tests. This is performed by the solution of the steady inverse heat transfer problem using these thermal images, resulting in qualitative heat source distributions; these are analyzed using the mean heat source gradients to identify the elements that can be considered hotspots. This procedure identified that the processor INTEL Core 2 Quad Q8400S contains one hotspot located in the center of its left… More >

  • Open Access

    ARTICLE

    ASETS-II OSCILLATING HEAT PIPE SPACE FLIGHT EXPERIMENT: THE FIRST SIX MONTHS ON ORBIT

    Brenton S. Tafta,*, Kevin W. Irickb

    Frontiers in Heat and Mass Transfer, Vol.12, pp. 1-7, 2019, DOI:10.5098/hmt.12.24

    Abstract On September 7th, 2017 the U.S. Air Force Research Laboratory launched the second Advanced Structurally Embedded Thermal Spreader (ASETSII) flight experiment to space on Orbital Test Vehicle 5. The ASETS-II experiment is made of three low-mass, low-cost oscillating heat pipes (OHPs) and an electronics/experiment control box. The three primary science objectives of the experiment are to measure the initial on-orbit thermal performance, to measure long duration thermal performance, and to assess any lifetime degradation. The three OHPs on ASETS-II are of varying configuration (center heating with single- and double-sided cooling) and working fluids (butane and R-134a) in order to isolate… More >

  • Open Access

    ARTICLE

    EFFECTS OF SERRATED PULSATING AIRFLOW ON LIQUID FILM EVAPORATION IN A VERTICAL CHANNEL: A NUMERICAL STUDY

    Changming Linga,b,*, Yin Zhonga,b

    Frontiers in Heat and Mass Transfer, Vol.14, pp. 1-6, 2020, DOI:10.5098/hmt.14.25

    Abstract Effects of serrated pulsating airflow on liquid film evaporation in a falling film channel was numerically studied based on a two-dimensional model. The mechanism of pulsating airflow evaporation was studied as the pulsating airflow swept across the vertical liquid film surface at the stagnant temperature. Effects of amplitude, frequency, and velocity of the serrated pulsating airflow at certain evaporation time on evaporation were analyzed. Compared with the uniform airflow, the highest relative evaporation of liquid film on vertical pipe inner surface was increased by about 0.3 %. When the airflow was pulsating, the cycle of vapor mass flow rate was… More >

  • Open Access

    ARTICLE

    CFD-BASED STUDY ON HEAT TRANSFER ENHANCEMENT BEHIND A PROJECTION IN A MINIATURIZED FLOW CHANNEL BY PULSATING FLOW

    Wakana Hiratsukaa , Takashi Fukueb,*, Hidemi Shirakawac, Katsuyuki Nakayamad, Yasushi Koitoe

    Frontiers in Heat and Mass Transfer, Vol.15, pp. 1-8, 2020, DOI:10.5098/hmt.15.16

    Abstract This paper describes a possibility of heat transfer enhancement in a mm-scale flow channel by using a combination of some projections and pulsating flow. The objective of this research is to develop a novel heat exchanger for miniaturized productions such as high-density packaging electronic equipment by applying pulsating flow to enhance heat transfer while inhibiting an increase of pressure drop. In order to evaluate the possibility of applying pulsating flow to miniature water channels, a three-dimensional flow and heat transfer analysis was performed. Heat transfer performance of a combination of pulsating water flow and a projection was investigated. The mechanism… More >

  • Open Access

    ARTICLE

    NUMERICAL ANALYSIS OF PASSIVE TWO PHASE FLUID FLOW IN A CLOSED LOOP PULSATING HEAT PIPE

    Roshan Devidas Bhagata,*, Samir J. Deshmukhb

    Frontiers in Heat and Mass Transfer, Vol.16, pp. 1-16, 2021, DOI:10.5098/hmt.16.23

    Abstract Numerical analysis of passive two phase fluid flow in a 3D Closed Loop Pulsating Heat Pipe (CLPHP) with turns in evaporator and condenser section is carried out. Water is used as working fluid. The volume of fluid model (VOF) is used to simulate passive two-phase fluid flow in a Closed Loop Pulsating Heat Pipe. Filling ratio (FR) of is kept in the range of 60 to 70%. The evaporator temperature is set in the range of 353 K. The condenser temperature is set in the range of 298 K. The contours of volume fraction water, wall temperature and contours of… More >

  • Open Access

    ARTICLE

    LOW-ORDER MODEL OF THE DYNAMICS AND START-UP OF A PULSATING HEAT PIPE

    Felix Schilya,∗, Wolfgang Polifkea

    Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-15, 2021, DOI:10.5098/hmt.17.16

    Abstract A simple open-loop pulsating heat pipe model is proposed, which allows to analytically determine the start-up behavior by a linear stability analysis. Two distinct types of instability can occur in such a pulsating heat pipe: oscillatory and non-oscillatory. This paper demonstrates that for bubbles consisting of non-condensible gas, large temperature gradients along the wall are required to achieve start-up, whereas start-up is fairly easy to achieve when there is only a single working medium that forms bubbles from its vapor. The study also finds that surface tension as such only influences start-up indirectly, while contact angle hysteresis dampens out any… More >

  • Open Access

    ARTICLE

    EFFECT OF RIB HEIGHT ON HEAT TRANSFER ENHANCEMENT BY COMBINATION OF A RIB AND PULSATING FLOW

    Shintaro Hayakawaa , Takashi Fukuea,*,† , Yasuhiro Sugimotoa , Wakana Hiratsukab , Hidemi Shirakawac , Yasushi Koitod

    Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-9, 2022, DOI:10.5098/hmt.18.29

    Abstract This paper describes the effects of a combination of rib and pulsating flow on heat transfer enhancement in an mm-scale model that simulates the narrow flow passages in cooling devices of downsized electronic equipment. This research aims to develop a novel water cooling device that increases heat transfer performance while inhibiting pumping power. Our recent study has reported that a combination of pulsating flow and rib could enhance heat transfer performance relative to the simple duct. In the present study, to verify the optimal rib height for improving heat transfer by pulsating flow, we evaluated the relationship between heat transfer… More >

  • Open Access

    ARTICLE

    Modified Garden Balsan Optimization Based Machine Learning for Intrusion Detection

    Mesfer Al Duhayyim1,*, Jaber S. Alzahrani2, Hanan Abdullah Mengash3, Mrim M. Alnfiai4, Radwa Marzouk3, Gouse Pasha Mohammed5, Mohammed Rizwanullah5, Amgad Atta Abdelmageed5

    Computer Systems Science and Engineering, Vol.46, No.2, pp. 1471-1485, 2023, DOI:10.32604/csse.2023.034137

    Abstract The Internet of Things (IoT) environment plays a crucial role in the design of smart environments. Security and privacy are the major challenging problems that exist in the design of IoT-enabled real-time environments. Security susceptibilities in IoT-based systems pose security threats which affect smart environment applications. Intrusion detection systems (IDS) can be used for IoT environments to mitigate IoT-related security attacks which use few security vulnerabilities. This paper introduces a modified garden balsan optimization-based machine learning model for intrusion detection (MGBO-MLID) in the IoT cloud environment. The presented MGBO-MLID technique focuses on the identification and classification of intrusions in the… More >

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