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INVESTIGATION ON THE CAPACITANCE FLOWMETER & DEVELOPMENT OF VOID FRACTION SENSOR FOR CRYOGENIC TWO-PHASE FLOW

2024-07-15T09:20:38Z

Title: INVESTIGATION ON THE CAPACITANCE FLOWMETER & DEVELOPMENT OF VOID FRACTION SENSOR FOR CRYOGENIC TWO-PHASE FLOW Authors: Archana, Mohan; Mathew, Skaria Abstract: Cryocoolers are devices that produce very low temperatures and provide adequate amount of cooling power at a specific location and hence can replace the conventional cryogenic fluids. The main difference between cryocoolers and cryogenic fluids is that cryocoolers can produce refrigeration at various low temperatures, while cryogenic fluids only provide refrigeration at specific temperatures, namely their boiling points. Cryocoolers can be classified into different types based on the heat exchangers used in them. They are regenerative and recuperative types. Regenerative type cryocoolers are further classified into three types namely, Stirling, Gifford McMahon (GM) and Pulse Tube. The CTI GM type cryocooler (Model: Cryodyne, Number:350C) had been chosen in our studies to understand its design, working and also to reverse engineer its development. One could learn the assembly of the system and also how it can be dismantled without damaging the components. After preparing the dimensional drawing of the displacer, Bakelite has been used for its fabrication, since it forms an equivalent substitute for the original Micarta material. The newly fabricated displacer housing was filled with the original regenerator materials and assembled into the coldhead housing. The temperature sensors were incorporated for the first and second stage cold heads. The system was tested for its performance to determine its lowest temperature reached. The regenerator materials and the sealings form the crucial components for the improved performance of the cryocooler. Both Teflon split rings and Rulon split rings have been used as sealings in our studies. Presently second stage temperature ~11.5K has been measured with lead as the regenerator material, with a water cooled 3kW helium compressor. On the other hand, with 1.5kW helium compressor, a temperature of 14.7K has been measured with lead as the regenerator material. With the same helium compressor, temperatures of 15.48K and 19.45K have been measured with Holmium copper and Erbium Nickel as regenerator materialrespectively. Since the above values are higher than those of with Lead as regenerator, we suspect the above regenerator materials have aged and are not performing satisfactorily. The first stage temperatures have been measured as 75.96 K and 58.93 K for Holmium copper and Erbium Nickel as second stage regenerator materials respectively. The first stage regenerator material used in the setup is copper meshes (< 200 mesh size). We have successfully designed and fabricated the displacer housing of the GM cryocooler system. Experiment have been performed using both labyrinth and non-labyrinth type housing. The performance of the system with indigenously designed displacer is quite satisfactory. Also, the theoretical analysis of the single stage GM Cryocooler has been attempted using the open-source regions software. By this analysis one can evaluate the cooling power, COP and inefficiency of the system as a function of various design and operational parameters. Following are the outcomes of the project. 1. Complete design drawings of the first and second stage displacer along with its housing. 2. Both Labyrinth type and non-labyrinth type displacers I have been designed, fabricated and tested. 3. Teflon silly rings are formed to perform better than the plastic sealing rings The results indicate that the performance of the regenerator materials such as Holmium Copper and Erbium Nickel is not satisfactory due to the aging effect and perhaps one should look for fresh regenerator materials.

DEVELOPMENT OF TWO STAGE GIFFORD McMAHON CRYOCOOLER

2024-07-15T09:15:09Z

Title: DEVELOPMENT OF TWO STAGE GIFFORD McMAHON CRYOCOOLER Authors: Rahul, R; Rijo Jacob, Thomas Abstract: Cryogenic fluids have significant growth in different industrial applications, including superconductivity, aerospace etc. Depending on the application, the cryogenic fluid flow's purpose varies greatly. Cryogens are required in the case of superconducting magnets in order to maintain the magnet material below a certain temperature and preserve the superconducting state. Currently, no one technology is capable of measuring two-phase flow throughout the entire range of flow conditions. Presenting the design and testing of the proposed two-phase flow-metering device is the goal. The concept is to use capacitance to measure the liquid's height at various locations in the channel by forcing the flow into both a laminar and stratified flow regime. In theory, the flow-rate can be inferred from these height measurements. The idea is a two- phase flow of vapor and liquid through small, parallel channels that produces a laminar, stratified flow that slopes at the liquid-vapor interface. Capacitance-liquid level devices are used in the channel to measure the liquid height. G10 printed circuit boards (PCBs) are used to create the channel walls, and the capacitor conductors are electroplated directly onto the boards to minimize channel intrusion.

NUMERICAL INVESTIGATIONS ON SYNTHETIC JET IMPINGEMENT COOLING USING MULTIPLE ORIFICE

2023-10-07T07:13:57Z

Title: NUMERICAL INVESTIGATIONS ON SYNTHETIC JET IMPINGEMENT COOLING USING MULTIPLE ORIFICE Authors: Vaishnav, S; Shafi, K A Abstract: A synthetic jet generally consists of a cavity with a driver attached on one side and an orifice on the opposite side. When the driver moves back and forth, the jet will generate an unsteady flow through the orifice and the flow will move downstream to a surface forming an impinging flow. When the jet is in the ejection cycle, the diaphragm will expel flow out from the orifice and form a vortex near the orifice. If the propulsion is large enough, the vortex will move downstream before the jet orifice flow reverses and starts to suck in flow. The computational process is carried out using the commercial software ANSYS Fluent. In this study, the heat transfer characteristics of synthetic jet impingement cooling with multiple orifice (2,4 and 16 orifices) are analyse with different operating frequencies (f=1Hz to f=5Hz and f=100Hz to f=500Hz) with different Reynolds number (Re=5000,10000 and 20000) well as Strouhal number (St=0.006 to St=0.030). The results demonstrate that high frequency synthetic jets show better heat removal capacity than lower frequency at the same Reynolds number. Also, the variation of area averaged Nusselt number depends on Strouhal number or dimensionless stroke length.

EFFECT OF CRYOGENIC TREATMENT ON THERMAL AND MECHANICAL PROPERTIES OF HEMP FIBER COMPOSITE PANELS

2023-10-07T07:08:04Z

Title: EFFECT OF CRYOGENIC TREATMENT ON THERMAL AND MECHANICAL PROPERTIES OF HEMP FIBER COMPOSITE PANELS Authors: Rahul, Raj; Shafi, K A Abstract: Natural fibres have been outstanding materials which are feasible and amble substitute for expensive, non-bio degradable and non-renewable synthetic materials so these organic/natural fibres can be used as replacement for synthetic fibers for various applications. Cryogenic treatment is a type of heat treatment process applied to materials at low temperatures in which fiber is treated at cryogenic temperatures, at this low temperature conditions, materials showcase some physiochemical changes The main objective of these works is to conduct cryogenic treatment on hemp fiber and to study the effect of cryogenic treatment on thermal, mechanical and water absorption properties of hemp fiber reinforced epoxy composite panels. Physical properties such as functional groups of fabrics were studied and compared using Fourier Transform Infrared Spectroscopy (FTIR). It shows treatment on fiber have substantially increased the number of hydrogen bonding in cellulose, which lead to increase in stiffness of the fabric. The thermal behaviour of untreated and treated hemp fiber was studied using the techniques of thermo gravimetric analysis (TGA) and differential thermo gravimetric analysis (DTG). It is observed that after cryogenic treatment, hemp fiber's thermal stability has been significantly enhanced. Mechanical properties such as tensile and flexural strength of Hemp/epoxy panels are studied under untreated and cryogenic treated condition and the result show improvement in mechanical properties under cryogenic treatment. Improvement in mechanical properties was observed in cryogenic treated hemp composite due to increased frictional bond in the composite interface. Thermal conductivity of panels was measured using guarded hot plate method and the results shows decrease in thermal conductivity after cryogenic treatment. Water absorption rate of the fiber increases with time due to hygroscopic nature of fiber.Cryogenic treated hemp fiber shows 12% reduction in percentage of water absorption compared to untreated hemp fiber. These findings indicate hemp fabric as an alternative bio degradable material with greater thermal stability and physical qualities than synthetic materials for engineering applications