Boiling aspects analysis of refrigerant and binary mixtures in microscale heat transfer

(Past Activity)

Activity description
Experimental facility (Test Section - Test Matrix)

Activity responsible: Dr. Giuseppe Zummo
Address: ENEA C.R. Casaccia,Energy Department, Institute of Thermal Fluid Dynamics, Via Anguillarese 301 (S.P. 092), 00060 S. M. di Galeria RM, Italy
Phone: +39 06 3048.4567 Fax: +39 06 3048.3026


Activity description

Objectives of this experimental activity are here summarised:

  1. to obtain extensive heat transfer data (in Single Phase convection end Two-Phase flow boiling) over large parameter ranges of refrigerants flow in microtubes
  2. to obtain extensive pressure drop data of refrigerants flow in microtubes
  3. to verify heat transfer correlations in microtubes configuration
  4. to verify pressure drop correlations in microtubes.


Experimental facility - Test loop

The test loop, called MISHTRA (Micro Scale Heat TRAnsfer) has been designed and built with with the following characteristics:

Flow rate: up to 100 L/h
Pressure: up to 30 bar
Temperature: up to 150 C
DC power: up to 50 V and 1500 A.


Experimental facility - Test section

Because the tested tubes are relatively small, direct measurement of thermal-hydraulic parameters is difficult and is subjected to large error. Therefore, in order to obtain reasonable measurements, 6 microtubes, each having the same diameter and length, are put together to form the test section, as shown in the picture.
At present, indirect heating of the test micropipes has been set up using condensing steam, in order to have a direct evaluation of the wall temperature (without thermocouples soldered on the microtubes surface) and thus the heat transfer coefficient. The experimental programme is carried out on the MISHTRA facility.


Experimental facility - Test matrix

At present, experiments are focused on single phase pressure drop and heat transfer with the following test parameters range:

D = 0.06, 0.13, 0.25 and 0.50 mm
Z = 0.1 m
U = 0.25 – 8.0 m/s
P = 20 – 30 bar
Tin = 20 – 80 C
Flow direction: horizontal


Electronic cooling
Compact and miniature heat exchangers
Refrigeration and air conditioning systems