Comparative Study on a Straight and Helical Capillary Tube for CO2 and R22 Refrigerant

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Pravin Jadhav ◽  
Neeraj Agrawal
Keyword(s):  
Numerical Model ◽  
Comparative Study ◽  
Capillary Tube ◽  
Tube Diameter ◽  
Tube Length ◽  
Percentage Reduction ◽  
Basic Principles ◽  
Conservation Of Mass ◽  
Coil Diameter ◽  
Mass Flowrate

Abstract A comparative study has been carried out on the adiabatic straight and helical capillary tube, using a CO2 and R22 refrigerant. The numerical model for CO2 and R22 is developed using the basic principles of conservation of mass, momentum, and energy. The effect of coiling in the helical capillary tube is compared with a straight capillary tube for CO2 and R22 refrigerant. Compared with the straight capillary tube, the percentage reduction in mass flowrate in the helical capillary tube is calculated with a change in coil diameter, tube diameter, and length. As the coil diameter increases from 30 mm to 150 mm, the percentage reduction in mass is from 5.8% to 2.2% in CO2, and 5% to 1.6% in R22. For helical capillary tube with 50 mm coil diameter, as the tube diameter increases from 1 to 1.5 mm, the percentage reduction in mass flowrate with CO2 refrigerant is from 2.65% to 4.96%, however, for R22 it is from 2.43% to 4.24%. Similarly, as the capillary tube length increases from 1.3 m to 1.8 m, the percentage reduction in mass with CO2, with 50 mm coil diameter is 4.44–4.55%. However, the percentage reduction in mass with R22 is 3.71–3.85%. Moreover, compared with the straight capillary tube, the percentage reduction in length in a helical capillary tube with coil diameter 50 mm is 16% for CO2 and 9% for R22 refrigerant.

Choked Flow Behavior of CO2 Refrigerant Flowing Through the Spiral Capillary Tube

2020 ◽  
Vol 28 (03) ◽  
pp. 2050024
Author(s):  
Pravin Jadhav ◽  
Neeraj Agrawal
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Graphical Representation ◽  
Capillary Tube ◽  
Flow Behavior ◽  
Tube Diameter ◽  
Tube Length ◽  
Flow Conditions ◽  
Choked Flow

The flow characteristics of CO2 refrigerant are numerically studied for an adiabatic spirally coiled capillary tube employing choked flow conditions. The mass, momentum and energy conservation equations are used to develop a numerical model. The existing model is verified with the published results. The choked flow behavior at various geometric parameters viz. tube diameter and spiral pitch is studied. Similarly, the influence of these parameters on the mass flow rate through the tube is observed. A significant change in mass flow rate is due to a change in tube diameter, whereas a minimal variation is observed with the change in surface roughness and spiral pitch. Moreover, it is observed that the coiling effect has a significant influence on the flow behavior of the spiral capillary tube. As the pressure decreases, from unchoked to the choked pressure in the evaporator by 63.46%, the mass flow rate increases by 9.46% only. The capillary tube choking is circumvented by increasing spiral pitch, tube diameter and decreasing the length of the tube. A unique nomogram is developed that gives the best understanding of choked and unchoked flow conditions, that graphical representation is useful to design the spirally coiled capillary tube. By using that, the choked length is identified for the known mass flow rate, even more, the choked mass flow rate is known for a given tube length. Moreover, for the given tube length and evaporator temperature, a nomogram is useful to the known choked values of mass flow rate and exit values of the evaporator pressure and quality of refrigerant.

Experimental Investigation on Flow Characteristic of Stepped Capillary Tube for Heat Pump Type Air Conditioner with R410A

2014 ◽  
Vol 960-961 ◽  
pp. 643-647
Author(s):  
Yan Sheng Xu
Keyword(s):  
Mass Flow Rate ◽  
Heat Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tube ◽  
Coefficient Of Performance ◽  
Tube Length ◽  
Air Conditioner ◽  
Capillary Tubes ◽  
Tube Assembly

A stepped capillary tube consisting of two serially connected capillary tubes with different diameters is invented to replace the conventional expansion device. The mass flow rate of refrigerant R410A in stepped capillary tubes with different size were tested. The model of stepped capillary tube is proposed, and its numerical algorithm for tube length and mass flow rate is developed. The experimental results show that the performance comparing between stepped capillary tube system and capillary tube assembly system, the cooling capacity is reduced by 0.3%, the energy efficiency ratio (EER) is equal to each other, the heating capacity is increased by 0.3%, the coefficient of performance (COP) is decreased by 0.3%. That is to say, the performance index of the two kinds of throttle mechanism is almost identical. It indicates that the stepped capillary tube can replace the capillary tube assembly in the R410A heat pump type air conditioner absolutely. The model is validated with experimental data, and the results show that the model can be used for sizing and rating stepped capillary tube.

Abstract P211: N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (Ac-SDKP) Promotes Tube Formation in Human Coronary Artery Endothelial Cells

Hypertension ◽  
2016 ◽  
Vol 68 (suppl_1) ◽  
Author(s):  
Ginette Bordcoch ◽  
Pablo Nakagawa ◽  
Cesar A Romero ◽  
Oscar A Romero
Keyword(s):  
Endothelial Cells ◽  
Coronary Artery ◽  
Capillary Tube ◽  
Tube Formation ◽  
Endothelial Cell Migration ◽  
Tube Length ◽  
Human Coronary Artery ◽  
Double Phase ◽  
Angiogenic Effect

Ac-SDKP is an endogenous peptide with anti-inflammation and anti-fibrotic effects in hypertensive and cardiovascular diseases. It is cleaved from Thymosin β4 (Tβ4) and hydrolyzed by angiotensin converting enzyme (ACE). Ac-SDKP plasma concentration increases after treatment with ACE inhibitors (ACEi) and some of the beneficial effects of ACEi treatment has been ascribed to Ac-SDKP. Ac-SDKP is a mediator of angiogenesis in in-vitro and in-vivo animal models. Ac-SDKP stimulates rodents derived immortalized aortic endothelial cells migration and capillary-like structures formation (tube formation). Similarly, Ac-SDKP increases capillary density after myocardial infarction in rats. The mechanism related to angiogenesis induced by Ac-SDKP is not known. Tβ4 (Ac-SDKP precursor) promotes endothelial cell migration and angiogenesis by the activation of the VEGF/AKT pathway. Our objective is to evaluate the Ac-SDKP pro-angiogenic effect in Human Coronary Artery Endothelial Cells (HCAEC) and the mechanism that regulates the angiogenic effect of Ac-SDKP. HCAEC do not produce VEGF, thus we hypothesize that Ac-SDKP increases VEGF expression in fibroblasts and that indirectly could promote capillary tube formation in endothelial cells. We used primary culture of rat cardiac fibroblast (RCF) and we treated these cells with 10nM Ac-SDKP for 24 hours. VEGF concentration in cell supernatant was measured by ELISA. Cells were starved without serum overnight before the Ac-SDKP treatment. For capillary tube formation assay, HCAEC cells were seeded into matrigel and incubated in presence of 10nM Ac-SDKP for 12 hours, pictures were taken by double phase contrast microscope and tube length was quantified with image J software and the results were expressed as percentage of control. After Ac-SDKP treatment, VEGF concentration did not increase in the supernatant of RCF (control: 0.12±0.07 vs. Ac-SDKP: 0.14±0.09 mg/ml; p=0.7). However, Ac-SDKP treatment induced the development of tube formation in HCAECs by 7±2% respect to control (p=0.037). We conclude that Ac-SDKP induces capillary tube formation not only in rodent but also in human derived endothelial cells. The mechanism by which Ac-SDKP promotes tube formation in HCAECs is still unknown.

scholarly journals Comparative study on destructive performance and energy absorption of aluminum tube by simulation and experiment

2020 ◽  
Vol 12 (5) ◽  
pp. 168781402092413
Author(s):  
Lai Hu ◽  
Jun Zha ◽  
Yaolong Chen
Keyword(s):  
Comparative Study ◽  
Energy Absorption ◽  
Simulation Analysis ◽  
High Energy ◽  
Low Energy ◽  
Tube Length ◽  
Thin Wall ◽  
Span Length ◽  
Aluminum Tube ◽  
High Energy Absorption

This study conducted an investigation on transverse quasi-static three-point loading on a circular aluminum tube and its characteristic plastic failure and energy-absorption behaviors. The thin wall thickness of the aluminum tube, the various diameter and thickness ratios ( D/ t) of the tube, and the tube length are important control parameters. Experimental data for different span length and thickness ratios of the tube were characterized and correlated to its plastic collapse behavior. A simulation model by computational analysis using ANSYS was also conducted as a comparative study. The results of the study found that transverse three-point bend loading (ASTM F290) of a circular aluminum tube underwent different stages of deformation, from initial pure crumpling to crumpling and bending, and finally, structural rupture. The results of master curve analysis found that regions of high energy absorption and low energy absorption can be classified with respect to the characteristic tubular deformation. High energy absorption deformation is correlated with a short span length and higher D/ t ratio, and vice versa for low energy absorption deformation of the circular aluminum tube. Simulation analysis also predicted similar characteristic trends of deformation behavior in the experiment, with a less than 3% average coefficient of variation.

Numerical Study on Choked Flow of CO2 Refrigerant in Helical Capillary Tube

2018 ◽  
Vol 26 (03) ◽  
pp. 1850027 ◽  
Author(s):  
Pravin Jadhav ◽  
Neeraj Agrawal
Keyword(s):  
Fluid Dynamics ◽  
Present Model ◽  
Capillary Tube ◽  
Numerical Study ◽  
Fundamental Principle ◽  
Tube Diameter ◽  
Published Data ◽  
Flow Conditions ◽  
Pressure Drops ◽  
Choked Flow

This paper presents a numerical study on an adiabatic helical capillary tube employing homogenous and choked flow conditions of a CO2 transcritical system. The theoretical model is based on the fundamental principle of fluid dynamics and thermodynamics. The result of the present model validates with the previously published data. The influence of operating and geometric parameters on the performance of the capillary tube has been evaluated. Flow characterizations of choked and unchoked flow conditions are determined. As the evaporator pressure drops, from unchoked condition to choked state, the percentage change in mass flow rate is minimal. A simulation graph is developed which has been helpful for the design of the helical capillary tube. The choked flow condition in a capillary tube is avoided by either increasing tube diameter of the fixed length tube or decreasing the length of the fixed tube diameter.

Simulation and Optimization of Homogeneous Decomposition of Sulfur Trioxide Gas on a Catalytic Surface

2005 ◽  
Author(s):  
Kiran K. Muramalla ◽  
Yitung Chen ◽  
Anthony E. Hechanova
Keyword(s):  
Heat Exchanger ◽  
Numerical Model ◽  
Surface Temperature ◽  
Flow Rate ◽  
Sulfur Trioxide ◽  
Tube Length ◽  
Two Dimensional ◽  
Wall Surface ◽  
Wall Surface Temperature ◽  
Homogeneous Decomposition

This paper deals with the development of a two-dimensional numerical model to predict the wall-catalyzed homogeneous decomposition of sulfur trioxide in a tubular component geometry for the production of hydrogen by the sulfur-iodine thermochemical water splitting cycle, a candidate cycle in the U.S. Department of Energy Nuclear Hydrogen Initiative. The reacting fluid is a mixture of sulfur trioxide gas and water vapor inside the tubes of a heat exchanger. The heat exchanger is made of Incoloy alloy 800H with ALFA-4 coated on the inner walls which acts as a catalyst. Decomposition of sulfur trioxide depends on many different parameters such as wall surface temperature, mole flow rate of the reacting mixture, diameter of the reactor tube, length of the reactor tube, operating pressure and inlet temperature of the reacting mixture. The effects of wall surface temperature, diameter of the reactor tube and mole flow rate on the decomposition of sulfur trioxide were investigated using a two-dimensional numerical model using Computational Fluid Dynamics (CFD) techniques. The preprocessor GAMBIT was used to create a computational mesh and the CFD software package FLUENT 6.2.16 [1] which is based on finite volume methods was used to simulate the problem. Both FLUENT 6.2.16 and Tecplot 10.0 are used to post process the problem.

Standard Rating Charts for Low Global Warming Potential Refrigerants Flowing Through Adiabatic Helical Capillary Tube

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Badrish Pandey ◽  
Desireddy Shashidhar Reddy ◽  
Mohd. Kaleem Khan ◽  
Manabendra Pathak
Keyword(s):  
Global Warming ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Global Warming Potential ◽  
Capillary Tube ◽  
Prediction Algorithm ◽  
Mean Deviation ◽  
Coil Diameter ◽  
Low Global Warming Potential

The present research work is undertaken to develop ASHRAE like standard rating charts for currently used refrigerants R-134a and R-410A and their potential low global warming potential (GWP) substitutes R-1234yf and R-32, respectively. A self-adjustable mass prediction algorithm has been developed using an averaging technique. Based on this, a matlab code dynamically linked to refprop v. 9.0 software has been developed that solves governing equations of mass, momentum, and energy. Two-phase flow inside the capillary tube is assumed homogeneous and metastability is ignored in the proposed model. The proposed numerical models are in good agreement with the available experimental data with overall percentage mean deviation is less than 6%. Coil diameter plays an important role in adjusting the mass flow rate in the helical capillary tube. Coiling of capillary tube causes an increase in friction pressure drop and a reduction in refrigerant mass flow rate. It has been found that the mass flow rate reduces by about 5% as coil diameter is reduced from 120 to 20 mm.

scholarly journals DESIGN AND STUDY OF DIMENSIONAL PARAMETERS INFLUENCE ON VORTEX TUBE BEHAVIOR

2019 ◽  
Vol 18 (2) ◽  
pp. 13
Author(s):  
F. P. Branco ◽  
E. D. Buchelt ◽  
F. M. Barbosa ◽  
B. P. Rosa ◽  
D. J. Laporte
Keyword(s):  
Vortex Tube ◽  
Tube Diameter ◽  
Compressed Air ◽  
Tube Length ◽  
Electronic Systems ◽  
Machining Processes ◽  
Cold Air ◽  
Air Temperatures ◽  
Small Influence ◽  
Dimensional Parameters

Vortex tube is a thermodynamic device, with no moving parts, applied to separate hot and cold air from compressed air injected into the tube. It has many applications in the industry, for example, among others, it can be mentioned electronic systems cooling, machining processes cooling and environmental chambers. This paper presents the design and tube dimensioning based on parameters and data found in the literature. Therefore, a prototype has been made and tested, which allowed the understanding of the influence of internal tube diameter and width on the hot and cold air temperatures while submitted to compressed air with pressure varying from 1 to 2.5bar. Results of tested configurations indicates that the relation between tube length and diameter (L/D) has small influence on vertex tube behavior, meanwhile, 3/8” tube diameter shows lowest temperatures on cold flow (-6.5°C, -8.0°C and -8.5°C) and higher COP (≈ 0.15).

Sign in / Sign up

Export Citation Format

Share Document