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Thermal And Hydraulic Performance Of A Novel Evaporator Coil For Refrigeration Systems
Full text linkWith increasing energy cost and constraints on emission standards, there is a strong need to reduce energy consumption and/or increase equipment efficiency. Refrigeration systems are the third largest use of electricity globally, consuming 1.8 trillion kWh annually. There have been some recent developments in energy efficient refrigeration systems, driven by rising price of electricity and increasing environmental concerns. However, refrigeration equipment remains highly energy demanding. One of the key sources of high energy consumption is the need to periodically heat up the system to defrost the evaporator coils. To solve this problem and reduces the energy demand of the defrosting system, a new evaporator coil is designed which can be defrosted at a fraction of the required energy. The new coil is a finless spiral-helical coil that uses a patented defrost/de-icing technology. In this paper, experimental investigations are presented that compares the thermal and hydraulic performances of a conventional finned-tube coil with a finless coil for a small cooling capacity unit. An experimental setup is designed and built to measure the cooling capacity and air pressure drop of both finned-tube and finless evaporator coils. The results show a higher cooling capacity per surface area for the new finless coil than the finned-tube one and that is mainly due to its higher heat transfer coefficient; making it suitable for this application
Gas Thruster Calibration For Satellite Simulators On An Air Bearing Table
Full text linkThis paper covers a simple method of calibration for gas thrusters for the application of simulated space flight. Gas thrusters are a common means of controlling spacecraft, and proper calibration of such thrusters is essential to ensure accurate and stable control of the spacecraft. Satellite simulators attempt to replicate the behaviours of satellites in flight using a 3 degree of freedom air bearing table, which allows for frictionless flight, and gas thrusters to emulate the flight dynamics
An Experimental Evaluation On Air Conditioning Performance With Vairtex Air Director Applied On Residential Condenser Unit
Full text linkPaper presented at 2018 Canadian Society of Mechanical Engineers International Congress, 27-30 May 2018.Thermodynamic performance measurements of a 1.5 ton residential air conditioning system and fluid flow hot-wire velocity measurements at the outlet of the condenser were performed with and without an add-on device (VairTEX Air Director added on top of the condenser unit). The Air Director modified all three velocity components at the condenser exit. Data from hot-wire confirmed the Air Director reduced the radial component while enhancing swirling factor and adding 48.7% volumetric flow rate across the condenser unit. By streamlining the flow, the Air Director led to an improvement of 5% in terms of overall coefficient of performance of the air conditioning unit and 4.5% reduction in compressor power consumption
A Finite Element Model To Predict The Effect Of Porosity On Elastic Modulus In Low Porosity Materials
Full text linkThe effect of porosity on elastic modulus in low porosity materials is investigated. First, several models used to predict the reduction in elastic modulus due to porosity are compared with a compilation of experimental data to determine their ranges of validity and accuracy. The overlapping solid spheres model is found to be most accurate with the experimental data and valid between 3-10% porosity. Next, a FEM is developed with the objective of demonstrating that a macroscale plate with a center hole can be used to model the effect of microscale porosity on elastic modulus. The FEM agrees best with the overlapping solid spheres model and shows higher accuracy with experimental data than the overlapping solid spheres model
Influence Of Porosity And Alloy Addition On The Wear Behaviour Of A Sinter-Forged C45 Steel Using Taguchi Method
Full text linkElemental powders of Atomized Iron (Fe), Carbon (C) and Molybdenum (Mo) were weighed and mixed in a pot mill to yield the composition of C45, C45-1%Mo and C45-2%Mo Steels, then compacted and sintered. The Sintered preforms had a density- 75% of the Theoretical Density. Then the Sintered preforms were subjected to densification to get two densities- 80% and 85% of the theoretical density through Forging. The sintered and densified preforms of alloy steels are subsequently machined to get the required test specimens. The experiments were conducted on a pin-on-disc Tribometer, conforming to ASTM G99 standards, on a rotating EN32 disc. Using Minitab 16 software, the Dry Sliding wear experiments were planned using L27 Orthogonal Array. The % Theoretical Density of the Specimens, % Mo Addition, Load and Sliding Speed were taken as input parameters, mass loss was the output parameter. It was observed that the increasing density of alloy steels adversely affects the wear resistance of the alloy steels and mass loss is increased. It was found that the addition of Mo significantly improves the wear resistance of the alloy steels irrespective of the densities due to hard phase carbides present in the microstructure. Empirical correlations for mass loss with respect to input parameters had been developed using Regression Analysis. In the case of Mo added alloy, Mo particulates embedded between the ferrite-pearlite grains are observed from the microstructure
