Micro Cryogenic Coolers With Mixed Refrigerants

2013 ◽  
Author(s):  
Ryan Lewis ◽  
Yunda Wang ◽  
Paul Schroeder ◽  
Collin Coolidge ◽  
Ray Radebaugh ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Channel Flow ◽  
Pressure Ratio ◽  
Maximum Flow ◽  
Cooling Power ◽  
Micro Channel ◽  
Standard Ml ◽  
Micro Channels ◽  
Flow Through ◽  
Cryogenic Cooler

A number of small electronic devices benefit from micro-scale low temperature operation. Recently we have developed micro cryogenic coolers (MCCs) using a low-pressure, mixed-refrigerant Joule-Thomson cycle. The cryocoolers utilizes a MEMS-enabled gas compressor coupled to a micro cold stage. Two cold stages have been developed: one which uses a fiber-enabled heat exchanger assembled to a micro-machined throttling valve, and another which uses a MEMS-based heat exchanger. A microcompressor has been developed which uses MEMS-based check valves coupled to a membrane, which is actuated with a mechanically amplified piezoelectric amplifier. The compressor measures a volume 15 mL, can generate a pressure ratio of 6:1 and a maximum flow-rate of 60 standard mL/min. The complete cryocooler has reached low temperatures of 177 K, although temperature instability has been an issue, due to 2-phase flow through the micro-channels. This paper will cover the development and testing of the micro cryogenic cooler, as well as an analysis of the micro channel flow. A proper understanding of the micro-channel flow allows us to design refrigerant mixtures to improve the cooling power, and modify the cooler to eliminate temperature instabilities.

An Investigation on Micro Slip Flows in Micro Channels

2010 ◽  
Author(s):  
Gh. Reza Salehi ◽  
Masoud JalaliBidgoli ◽  
Saeed ZeinaliDanaloo ◽  
Kazem HasanZadeh
Keyword(s):  
Flow Rate ◽  
Pressure Ratio ◽  
Slip Flow ◽  
Accommodation Coefficient ◽  
Flow Rate Ratio ◽  
Numerical Representation ◽  
Micro Channel ◽  
Parallel Plates ◽  
Dimensionless Numbers ◽  
Micro Channels

In this paper, distributions of velocity and flow rate of micro channels are studied. Moreover, the parameters which influence them were also discussed, as well as their effects and relevant curves. In the Analytical study, the governing equation in specific micro flows is obtained. This equation is specifically investigated for slip flow in two micro parallel plates (micro channel).At the next step numerical representation shows the influence of the related parameters in micro channel flow such as Knudsen number, thermal -accommodation coefficient, mass flow rate ratio and pressure ratio (outlet to inlet), Tangential Momentum Accommodation Coefficient with relative curves, and flow rate distribution in slippery state to no slip state has been compared as the another part of this solution. Finally, the results of investigating parameters and dimensionless numbers in micro channels are reviewed.

A Study on the Strength under Pressure of Micro Heat Exchanger

2006 ◽  
Vol 326-328 ◽  
pp. 265-268
Author(s):  
Taek Joon Son ◽  
Young Shin Lee
Keyword(s):  
Stainless Steel ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Structural Analysis ◽  
Thin Plate ◽  
Thin Plates ◽  
Micro Channel ◽  
Design Guideline ◽  
Micro Heat Exchanger ◽  
Micro Channels

The strength of micro heat exchanger under pressure is studied in this paper. Micro heat exchanger is made with brazing technology. It is constructed of stainless steel thin plates with micro channels and in/out port for fluid flow. Micro channels in thin plates are formed by etching and all parts including thin plates are joined by brazing. The study on the strength under pressure is performed by structural analysis. For structural analysis, one layer of micro heat exchanger body is considered. It is composed of thin plate with micro channel and brazing filler which is used to join thin plates. This paper shows the tendency of stress behavior and gives design guideline of micro heat exchanger.

Coupled Heat Transfer and Hydraulic Modeling of an Experimental Printed Circuit Heat Exchanger Using Finite Element Methods

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Ian W. Jentz ◽  
Mark H. Anderson
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Heat Exchanger ◽  
Hydraulic Modeling ◽  
Design Tool ◽  
Micro Channel ◽  
Printed Circuit ◽  
Coupled Heat Transfer ◽  
Computational Overhead ◽  
Micro Channels

Abstract The Homogenized Heat Exchanger Thermohydraulic (HHXT) modeling environment has been developed to provide thermodynamic modeling of printed circuit heat exchangers (PCHEs). This finite element approach solves solid conduction and fluid thermohydraulics simultaneously, without the need to mesh the minuscule micro-channels of a PCHE. The model handles PCHE features such as headers, solid side walls, and channel inlet and outlet regions, in addition to the micro-channel core. The HHXT model resolves PCHE thermohydraulics using simple model definitions and minimum computational overhead, making it an ideal design tool. This work introduces the thermohydraulic model at the core of HHXT. The homogenization approach used in the model occupies a medium between simplified linear analyses of heat transfer within a PCHE and the brute force of a fully resolved finite element, or computational fluid dynamics, model. An example problem modeling an experimental PCHE is presented. The ability of the HHXT model to simulate fluid flow through a directional varying micro-channel core of two heat-exchanging streams is demonstrated. The HHXT model is being distributed for free within the research community.

scholarly journals Elastic Turbulence of Aqueous Polymer Solution in Multi-Stream Micro-Channel Flow

Micromachines ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 110 ◽  
Author(s):  
Jiayan Tai ◽  
Yee Cheong Lam
Keyword(s):  
Flow Field ◽  
Channel Flow ◽  
Flow Instability ◽  
Flow Behavior ◽  
Power Spectra ◽  
Micro Channel ◽  
Polymer Molecules ◽  
Aqueous Solvent ◽  
Micro Channels ◽  
Flow Field Characteristics

Viscous liquid flow in micro-channels is typically laminar because of the low Reynolds number constraint. However, by introducing elasticity into the fluids, the flow behavior could change drastically to become turbulent; this elasticity can be realized by dissolving small quantities of polymer molecules into an aqueous solvent. Our recent investigation has directly visualized the extension and relaxation of these polymer molecules in an aqueous solution. This elastic-driven phenomenon is known as ‘elastic turbulence’. Hitherto, existing studies on elastic flow instability are mostly limited to single-stream flows, and a comprehensive statistical analysis of a multi-stream elastic turbulent micro-channel flow is needed to provide additional physical understanding. Here, we investigate the flow field characteristics of elastic turbulence in a 3-stream contraction-expansion micro-channel flow. By applying statistical analyses and flow visualization tools, we show that the flow field bares many similarities to that of inertia-driven turbulence. More interestingly, we observed regions with two different types of power-law dependence in the velocity power spectra at high frequencies. This is a typical characteristic of two-dimensional turbulence and has hitherto not been reported for elastic turbulent micro-channel flows.

Heat Transfer Experiments of Ethylene Glycol-Water Mixture in Multi-Port Serpentine Meso-Channel Heat Exchanger Slab

2010 ◽  
Author(s):  
Mesbah G. Khan ◽  
Amir Fartaj
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Ethylene Glycol ◽  
Test Fluid ◽  
Water Mixture ◽  
Micro Channel ◽  
Working Fluids ◽  
Micro Channels

In past few years, narrow diameter flow passages (≤3 mm) have attracted huge research attentions due to their several advantageous features over conventional tubes (≥6 mm) especially from the view points of higher heat transfer, lesser weight, and smaller device size. Several classifications of narrow channels, based on sizes, are proposed in the open literature from mini to meso and micro (3 mm to 100 μm). The meso- and micro-channels have not yet entered into the HVAC and automotive heat exchanger industries to the expected potentials to take the above-mentioned advantages. The reasons may be the limited availability of experimental data on pressure drop and heat transfer and the lack of consolidated design correlations as compared to what is established for compact heat exchangers. While a number of studies available on standalone single straight channels, works on multi-channel slab similar to those used as typical thermal heat exchanger core elements are inadequate, especially the research on multichannel serpentine slab are limited in the open literature. The 50% ethylene glycol and water mixture is widely used in heat exchanger industry as a heat transfer fluid. Studies of pressure drop and heat transfer on this commercially important fluid using narrow tube multi-channel slab is scarce and the availability of experimental data is rare in the open literature. Conducting research on various shapes of meso- and micro-channel heat exchanger cores using a variety working fluids are a definite needs as recommended and consistently urged in ongoing research publications in this promising area. Under present long-term project, an automated dynamic single-phase experimental infrastructure has been developed to carryout the fluid flow and heat transfer research in meso- and micro-channel test specimens and prototype microchannel heat exchanger using a variety of working fluids in air-to-liquid crossflow orientation. In the series, experiments have been conducted on 50% ethylene glycol and water solution in a serpentine meso-channel slab having 68 individual channels of 1 mm hydraulic diameter to obtain the heat transfer data and the general pressure drop nature of the test fluid. Current paper presents the heat transfer characteristics of ethylene glycol-water mixture and the Reynolds number effects on pressure drop, heat transfer rate, test specimen NTU and effectiveness, overall thermal resistance, and the Nusselt number.

Design and Development of a Low-Cost, High Temperature Silicon Carbide Micro-Channel Recuperator

2005 ◽  
Author(s):  
Merrill A. Wilson ◽  
Kurt Recknagle ◽  
Kriston Brooks
Keyword(s):  
Heat Transfer ◽  
Silicon Carbide ◽  
High Temperature ◽  
Heat Exchanger ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Ceramic Materials ◽  
Micro Channel ◽  
Micro Channels ◽  
Micro Turbine

Typically, ceramic micro-channel devices are used for high temperature heat exchangers, catalytic reactors, electronics cooling, and processing of corrosive streams where the thermomechanical benefits of ceramic materials are desired. These benefits include: high temperature mechanical and corrosion properties and tailorable material properties such as thermal expansion, electrical conductivity and thermal conductivity. In addition, by utilizing Laminated Object Manufacturing (LOM) methods, inexpensive ceramic materials can be layered, featured and laminated in the green state and co-sintered to form monolithic structures amenable to mass production. In cooperation with the DOE and Pacific Northwest National Labs, silicon carbide (SiC) based micro-channel recuperator concepts are being developed and tested. The performance benefits of a high temperature, micro-channel heat exchanger are realized from the improved thermal efficiency of the high temperature cycles and the improved effectiveness of micro-channels for heat transfer. In designing these structures, the heat and mass transfer within the micro-channels are being analyzed with heat transfer models, computational fluid dynamics models and validated with experimental results. As an example, a typical micro-turbine cycle was modified and modeled to incorporate this ceramic recuperator and it was found that the overall thermal efficiency of the micro-turbine could be improved from about 27% to over 40%. Process improvements require technical advantages and cost advantages. These LOM methodologies have been based on well-proven industry standard processes where labor, throughput and capital estimates have been tested. Following these cost models and validation at the prototype scale, cost estimates were obtained. For the micro-turbine example, cost estimates indicate that the high-temperature SiC recuperator would cost about $200 per kWe. The development of these heat exchangers is multi-faceted and this paper focuses on the design optimization of a layered micro-channel heat exchanger, its performance testing, and fabrication development through LOM methodologies.

The Evaporative Gas Turbine [EGT] Cycle

1997 ◽  
Author(s):  
J. H. Horlock
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Mass Flow ◽  
Power Output ◽  
Pressure Ratio ◽  
Temperature Drop ◽  
Optimum Pressure ◽  
Flow Through ◽  
Gas Turbine Exhaust ◽  
Gas Turbine Cycle

Humidification of the flow through a gas turbine has been proposed in a variety of forms. The STIG plant involves the generation of steam by the gas turbine exhaust in a heat recovery steam generator [HRSG], and its injection into or downstream of the combustion chamber. This increases the mass flow through the turbine and the power output from the plant, with a small increase in efficiency. In the evaporative gas turbine [or EGT] cycle, water is injected in the compressor discharge in a regenerative gas turbine cycle [a so-called CBTX plant-compressor [C], burner [B], turbine [T], heat exchanger [X]]; the air is evaporatively cooled before it enters the heat exchanger. While the addition of water increases the turbine mass flow and power output, there is also apparent benefit in reducing the temperature drop in the exhaust stack. In one variation of the basic EGT cycle, water is also added downstream of the evaporative aftercooler, even continuously in the heat exchanger. There are several other variations on the basic cycle [e.g. the cascaded humidified advanced turbine (CHAT)]. The present paper analyses the performance of the EGT cycle. The basic thermodynamics are first discussed, and related to the cycle analysis of a dry regenerative gas turbine plant. Subsequently some detailed calculations of EGT cycles are presented. The main purpose of the work is to seek the optimum pressure ratio in the EGT cycle for given constraints [e.g. fixed maximum to minimum temperature]. It is argued that this optimum has a relatively low value.

Design of a Ceramic Heat Exchanger for Sulfuric Acid Decomposition

2006 ◽  
Author(s):  
Merrill A. Wilson ◽  
Charles Lewinsohn ◽  
James Cutts ◽  
Valery Ponyavin
Keyword(s):  
Heat Transfer ◽  
Sulfuric Acid ◽  
High Temperature ◽  
Heat Exchanger ◽  
Ceramic Materials ◽  
Compact Heat Exchanger ◽  
Micro Channel ◽  
Micro Channels ◽  
Macro Scale ◽  
Chemical Cycle

It has been proposed that compact ceramic heat exchangers can be used for high temperature, corrosive applications. This paper discusses the design development of a micro-channel heat exchanger for the decomposition of sulfuric acid as part of the hydrogen producing sulfur iodine thermo-chemical cycle. Corrosion studies of candidate materials indicate that ceramic materials have superior corrosion and creep resistance under these high temperature, high acid concentration environments. This compact heat exchanger utilizes micro-channels to enhance the heat transfer while maintaining low pressure drops within the system. Through modular stacking of these micro-channel networks, a "shell and plate" configuration enables the processing of commercial-scale processes. The ceramic materials provide for long-life applications. The design of the micro-channel features captures the enhanced heat transfer characteristics at the micro-scale; the modular assembly permits the integration into macro-scale processes. As a case study, the thermal performance and the economics were investigated to determine the feasibility of this compact heat exchanger for the hydrogen producing sulfur iodine thermo-chemical cycle. The results of this design effort with its associated performance goals and development status will be reported.

The Experiment for Vertical Rectangular Micro-Channel Flow Boiling

2014 ◽  
Vol 960-961 ◽  
pp. 451-455
Author(s):  
Dian Xun Li ◽  
Shu Sheng Zhang
Keyword(s):  
Channel Flow ◽  
Design Process ◽  
Flow Boiling ◽  
Groove Depth ◽  
Micro Channel ◽  
Experimental Equipment ◽  
Experiment System ◽  
Micro Channels

To further deepen exploration of boiling in micro-channels a set of experiment system for micro-channel flow boiling is homemade, which includes experimental equipment required and experimental pieces of the design process. The channel is width of 100mm, length of 1200mm, and the groove depth of 95mm. The gasket thickness is 0.5mm, 1.0mm, 1.5mm or 2.0mm.

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