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Title: Investigation of pressure drop in capillary tube for mixed refrigerant Joule-Thomson cryocooler

A capillary tube is commonly used in small capacity refrigeration and air-conditioning systems. It is also a preferred expansion device in mixed refrigerant Joule-Thomson (MR J-T) cryocoolers, since it is inexpensive and simple in configuration. However, the flow inside a capillary tube is complex, since flashing process that occurs in case of refrigeration and air-conditioning systems is metastable. A mixture of refrigerants such as nitrogen, methane, ethane, propane and iso-butane expands below its inversion temperature in the capillary tube of MR J-T cryocooler and reaches cryogenic temperature. The mass flow rate of refrigerant mixture circulating through capillary tube depends on the pressure difference across it. There are many empirical correlations which predict pressure drop across the capillary tube. However, they have not been tested for refrigerant mixtures and for operating conditions of the cryocooler. The present paper assesses the existing empirical correlations for predicting overall pressure drop across the capillary tube for the MR J-T cryocooler. The empirical correlations refer to homogeneous as well as separated flow models. Experiments are carried out to measure the overall pressure drop across the capillary tube for the cooler. Three different compositions of refrigerant mixture are used to study the pressure drop variations. Themore » predicted overall pressure drop across the capillary tube is compared with the experimentally obtained value. The predictions obtained using homogeneous model show better match with the experimental results compared to separated flow models.« less
Authors:
 [1] ; ;  [2]
  1. Mechanical Engineering Department, Indian Institute of Technology Bombay, Mumbai, MS 400 076 India and S. S. G. M. College of Engineering Shegaon, MS 444 203 (India)
  2. Mechanical Engineering Department, Indian Institute of Technology Bombay, Mumbai, MS 400 076 (India)
Publication Date:
OSTI Identifier:
22262744
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1573; Journal Issue: 1; Conference: Cryogenic engineering conference, Anchorage, AK (United States), 17-21 Jun 2013; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; AIR CONDITIONING; BUTANE; CAPILLARIES; ETHANE; FLOW MODELS; FLOW RATE; HEAT EXCHANGERS; METHANE; MIXTURES; PRESSURE DROP; PROPANE; REFRIGERANTS; REFRIGERATION; TUBES