H213 Analysis of the Emergency Core Cooling System without Electric Power by using the Two-phase Flow ejector

2011 ◽  
Vol 2011 (0) ◽  
pp. 365-366
Author(s):  
Masafumi Nakagawa ◽  
Chikara Sato
Keyword(s):  
Electric Power ◽  
Two Phase Flow ◽  
Cooling System ◽  
Phase Flow ◽  
Two Phase ◽  
Core Cooling

Control of Cold Plate Temperature in a Pumped Two Phase Flow

2019 ◽  
Author(s):  
Alok Sinha ◽  
Larry W. Byrd
Keyword(s):  
Feedback Control ◽  
Control Algorithm ◽  
Two Phase Flow ◽  
Cooling System ◽  
Output Feedback Control ◽  
Phase Flow ◽  
Cold Plate ◽  
Two Phase ◽  
Plate Temperature ◽  
The Heat Transfer Coefficient

Abstract One of the main goals of a pumped two-phase flow cooling system is to ensure that there is a two phase flow at the exit of the cold plate so that the heat transfer coefficient remains very high. To decrease the mass flow rate but still prevent dryout, there is a motivation to maintain the exit quality at roughly 0.6 to 0.7 for an unknown time-varying heat load. In this paper, a simple output feedback control algorithm is proposed to achieve this goal. A nonlinear model based on the conservation of mass, momentum, and energy is used. Steady state solutions and their stability are analyzed. Results from numerical simulations with R134a flow corroborate the validity of the proposed novel feedback control algorithm.

Numerical Analysis of Flow at Water Jacket of an Internal Combustion Engine

2011 ◽  
Vol 282-283 ◽  
pp. 702-705 ◽  
Author(s):  
De Zhi Zhang ◽  
Ying Ai Jin ◽  
De Yuan Su ◽  
Qing Gao
Keyword(s):  
Two Phase Flow ◽  
Cooling System ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Phase Flow ◽  
Three Dimensional Model ◽  
Two Phase ◽  
Water Jacket ◽  
Model And Simulation

With the increasing degree of the enhancement of engine, engine cooling system design is considered particularly important. This paper used an established three-dimensional model of an engine water jacket to study, and used UDF function in the two-phase flow of the CFD, describe the mathematical model and simulation the engine at different operating conditions, and get the water jacket flow rate transfer thermal process. Finally, the results of the relationship between the engine water jacket of boiling heat transfer and flow velocity have been studied, and the importance of using two-phase flow model has been summarized.

Cooling Characteristics of Ultrafine Cryoprobe Utilizing Convective Boiling Heat Transfer in Microchannel

2010 ◽  
Author(s):  
Junnosuke Okajima ◽  
Shigenao Maruyama ◽  
Hiroki Takeda ◽  
Atsuki Komiya ◽  
Sangkwon Jeong
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Boiling Heat Transfer ◽  
Two Phase Flow ◽  
Cooling System ◽  
Capillary Tube ◽  
Phase Flow ◽  
Two Phase ◽  
Convective Boiling

This paper describes a novel cooling system to be applied in cryosurgery. An ultrafine cryoprobe has been developed to treat small lesions which cannot be treated by conventional cryoprobes. The main problem of the ultrafine cryoprobe is the reduction of the heat transfer rate by the small flow rate due to the large pressure drop in a microchannel and the large ratio of the surface area to the volume. In order to overcome these problems, we utilized boiling heat transfer in a microchannel as the heat transfer mechanism in the ultrafine cryoprobe. The objectives of this paper are to develop an ultrafine cryoprobe and evaluate its cooling characteristics. The ultrafine cryoprobe has a co-axial double tube structure which consists of inner and outer stainless steel tubes. The outer and inner diameters of the outer tube are 0.55mm and 0.3mm, respectively. The outer and inner diameters of the inner tube are 0.15mm and 0.07mm, respectively. The inner tube serves as a capillary tube to change the refrigerant from liquid state to two-phase flow. Furthermore, two-phase flow passes through the annular passage between the inner and out tube. The hydraulic diameter of the annular passage is 0.15mm. Furthermore, HFC-23 (Boiling point is −82.1°C at 1atm) is used as the refrigerants. The temperature of the ultrafine cryoprobe was measured. The lowest temperatures were −45°C in the insulated condition and −35°C in the agar at 37°C (which simulates in vivo condition). Furthermore, the frozen region which is generated around the ultrafine cryoprobe was measured 5mm from the tip of cryoprobe at 120s, and resulted to be 3mm in diameter. Moreover, the change of the refrigerant state is calculated by using the energy conservation equation and the empirical correlations of two-phase pressure drop and boiling heat transfer. As a result, the refrigerant state in the ultrafine cryoprobe depends on the external heat flux. Finally, the required geometry of the ultrafine cryoprobe to make high cooling performance is evaluated.

scholarly journals Computer cooling using a two phase minichannel thermosyphon loop heated from horizontal and vertical sides and cooled from vertical side

2010 ◽  
Vol 31 (4) ◽  
pp. 51-59 ◽  
Author(s):  
Henryk Bieliński ◽  
Jarosław Mikielewicz
Keyword(s):  
Heat Transfer ◽  
Personal Computer ◽  
Two Phase Flow ◽  
Cooling System ◽  
Cooling Capacity ◽  
Phase Flow ◽  
Two Phase ◽  
Vertical Side ◽  
Horizontal Side ◽  
Energy Balances

Computer cooling using a two phase minichannel thermosyphon loop heated from horizontal and vertical sides and cooled from vertical sideIn the present paper it is proposed to consider the computer cooling capacity using the thermosyphon loop. A closed thermosyphon loop consists of combined two heaters and a cooler connected to each other by tubes. The first heater may be a CPU processor located on the motherboard of the personal computer. The second heater may be a chip of a graphic card placed perpendicular to the motherboard of personal computer. The cooler can be placed above the heaters on the computer chassis. The thermosyphon cooling system on the use of computer can be modeled using the rectangular thermosyphon loop with minichannels heated at the bottom horizontal side and the bottom vertical side and cooled at the upper vertical side. The riser and a downcomer connect these parts. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop is based on mass, momentum, and energy balances in the evaporators, rising tube, condenser and the falling tube. The separate two-phase flow model is used in calculations. A numerical investigation for the analysis of the mass flux rate and heat transfer coefficient in the steady state has been accomplished.

Thermophysical Properties of Two-Phase Refrigerant Based Nanofluids in a Refrigeration Cycle

2016 ◽  
Author(s):  
Bilgehan Tekin ◽  
Almila G. Yazicioglu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermophysical Properties ◽  
Base Fluid ◽  
Two Phase Flow ◽  
Cooling System ◽  
Heat Transfer Analysis ◽  
Refrigeration Cycle ◽  
Phase Flow ◽  
Two Phase

Nanofluids are a class of fluids with nanoparticles suspended in a base fluid. The aim for using nanofluids is often to improve the thermophysical properties of the base fluid so as to enhance the energy transfer efficiency. As the technology develops; the size of devices and systems needs to get smaller to fulfill the engineering requirements and/or to be leading among competitors. The use of nanofluids in heat transfer applications seems to be a viable solution to current heat transfer problems, albeit with certain limitations. As an enhancing factor for the thermal conductivity of the base fluid, nanofluids are considered to be use in cooling system applications. For these applications, the base fluid, the refrigerant, exists as a two-phase liquid-vapor mixture in parts of the refrigeration cycle. To analyze, design and optimize the cycle in such applications, the thermophysical properties of the refrigerant based nanofluids for two-phase flow of refrigerant are needed. There are different models present in the literature derived for the thermophysical properties of nanofluids. However, a majority of the existing models for nanofluid thermophysical properties have been proposed for water- and other liquids-based nanofluids, through theoretical, numerical and experimental research. Therefore, the existing models for determination of the nanofluid thermophysical properties are not applicable for refrigerant based nanofluid applications when the results are compared. Thus, in this work, a new model is derived for the thermal conductivity and viscosity of refrigerant based nanofluids, using existing data from both heat transfer and thermophysical property measurement experiments. The effect of the nanoparticles on heat transfer in two phase flow of the refrigerant is considered by applying the two phase heat transfer correlations in the literature to experimental data. As a result, the thermophysical properties of the known states are determined through known heat transfer performance. Even though the model is developed from the analysis of flow in an evaporator and flow in a single tube with evaporating refrigerant, it is aimed to cover the flows in both evaporator and condenser sections in a vapor compression refrigeration cycle to provide the necessary models for thermophysical properties in heat transfer devices which will allow the design of both cycle and evaporator or condenser in terms of sizing and rating problems by performing heat transfer analysis and/or optimization. The model can also be improved by considering the effects of slip mechanisms that lead to slip velocity between the nanoparticle and base fluid.

Characteristics of Downcomer Boiling Phenomena During the Reflood Phase of a Postulated Large Break LOCA for the APR1400

2006 ◽  
Author(s):  
Byong-Jo Yun ◽  
Dong-Jin Euh ◽  
Won-Man Park ◽  
Young-Jung Youn ◽  
Chul-Hwa Song
Keyword(s):  
Two Phase Flow ◽  
Transient Behavior ◽  
Visual Observation ◽  
Test Facility ◽  
Phase Flow ◽  
Pressurized Water Reactor ◽  
Two Phase ◽  
Pressurized Water ◽  
Flow Parameters ◽  
Core Cooling

Downcomer boiling phenomena in a conventional pressurized water reactor have an important effect on the transient behavior of a postulated large-break LOCA (LBLOCA), because it can degrade the hydraulic head of the coolant in the downcomer and consequently affect the reflood flow rate for a core cooling. To investigate the thermal hydraulic behavior in the downcomer region, a test program for a downcomer boiling is being progressed in the reflood phase of a postulated LBLOCA. For this, the test facility was designed as a one side heated rectangular test section which adopts a full-pressure, full-height, and full-size downcomer-gap approach, but with the circumferential length reduced 47.08-fold. The test was performed by dividing it into two-phases: (I) visual observation and acquisition of the global two-phase flow parameters and (II) measurement of the local two-phase flow parameters on the measuring planes along five elevations. In the present paper, the test results of Phase-I and parts of Phase-II were introduced.

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