Experimental investigate to obtain the effectiveness of regenerator using Air.

*
Corresponding author e-mail: dakshaahir@gmail.com Journal access: www.ijesft.com
Tel.: +91 9427252888 © 2015 A D Publication. All rights reserved
ID:IJESFT20150101004 January 2015
International Journal of
Engineering Science and Futuristic Technology
A Peer-reviewed journal
ISSN : 2454-1125
IJESFT 01 (2015) 024-033
Experimental investigate to obtain the effectiveness of regenerator
using Air.
D P Bhadarka *
1Department of Mechanical Engineering, R C Technical Institute , Ahmedabad , Gujarat, India
A B S T R A C T : The regenerator is a kind of heat exchanger that provides a way to get the gas to the low
temperature with as much potential work (cooling power) as possible without carrying a lot of heat
with it. It doesn’t put heat in or out of the system but it absorbs heat from the gas on one part of the
pressure cycle and returns heat to the gas on the other part.
More recent applications of regenerators in cryogenic systems can be found in small
cryogenic refrigerators (cryocoolers). Systems such as the Stirling Gifford-McMahon, pulse tube,
Solvay, Vuilleumier and magnetic cycle refrigerators all use either a static or rotary regenerator.
In fact, the success these coolers have achieved is directly related to the characteristics of compact
size and efficiency of the regenerator.
Regenerator effectiveness of 99% results in 21% loss of refrigeration effect, similarly
regenerator effectiveness of 98% results in 42% loss of refrigeration effect, with refrigeration
effectiveness of 95.238% the loss of refrigeration is 100%. i.e. no net cooling is produced.
In cryogenic applications the regenerator is typically made up of 100 to 500 meshes SS 304,
Phosphorous bronze screens or small lead spheres (150 to 300 micro meters) are used, that are
tightly packed together and held in place on either end in the same manner.
To develop experimental setup at our laboratory level by using air as working fluid and find
out the effectiveness of various regenerative materials is basic goal of this work.
© 2015 A D Publication. All rights reserved
Keywords: regenerator, effectiveness
1. Introduction
Due to various advantages & increasing demand of cryocooler, the efficiency of cryocooler is a critical issue.
Regenerator is a vital component of cryocooler and effectiveness of regenerator effect on overall performance of
the cryocooler. Many investigations over the past four decades have been performed to developed methods to
evaluating the performance of regenerators. Pressure drop through the porous structure & temperature
effectiveness in its thermal response contribute heavily towards a loss of performance in the regenerator.
Effectiveness of regenerator effect on overall performance of cryocoolers.
2. Test procedure
The test apparatus for evaluating the effectiveness of regenerator is shown in the fig 1 and the procedure is
explained in following paragraphs as explained below. The setup is for steady flow type of regenerators used in
pulse tube refrigerators.
The test apparatus for the calorimetric method consists of two regenerators with the warm (ambient
temperature) ends connected to a flow-reversing valve and the cold ends connected to a heat exchanger, which
is attached to a liquid nitrogen bath.

25 D P Bhadarka/ International Journal of Engineering Science and Futuristic Technology
Nomenclature
ε Effectiveness
NTU Number of heat transfer units
Cp Specific Heat
H Plank’s heat constant
Awg Area of wetted periphery
M Mass flow rate
Th1 Hot end temperature of hot fluid
Th2 Cold end temperature of hot fluid
Tk1 Hot end temperature of cold fluid
Tk2 Cold end temperature of cold fluid
Ie Inefficiency
Q measured boil off rate of liquid nitrogen
(ṁ)f Measured mass flow rate of the fluid passing
through regenerator
Tw Warm fluid inlet temperature
Tc Cold fluid inlet temperature
The LN2 bath is surrounded by a second vessel, also surrounding by vaccum chamber to eliminate all
external heat loads into the vessel ensure that the only evaporation of LN2 from the inner vessel is the result of
the regenerator losses absorbed in the heat exchanger. The apparatus operates by periodically flowing fluid
through a balanced pair of regenerators by means of a flow-reversing valve located at the warm end of the
regenerators.
After steady-state temperature profiles are established in each of the regenerators, the inefficiency is
determined by measuring the fluid flow through the regenerator and the boil-off of LN2.
From these two measured quantities, the regenerator inefficiency, Ie, is calculated from the following energy
balance equation:
3. Experimental setup diagrams
Fig 1 Test set up for regenerator effectiveness with component arrangement
 ( )p f w c
Q
Ie
mc T T



D P Bhadarka / International Journal of Engineering Science and Futuristic Technology 26
Fig 2 Original experimental setup
Fig 3 Drawing of fabricated parts assembly

4. procedure for evaluation of boil-off rate
The boil-off rate of LN2 at NBP can be calculated by following method when used water displacement flow
meter (pressure 10-6 mbar to 10-5 mbar).
Boil-off rate of LN2 at atmosphere pressure in m3 /sec.
t
ld
V
2
4/

Where,
d = inner diameter of measuring limb
l = displacement of water to be measured.
t = time in 60 second
The boil-off rate of LN2 at NBP can be calculated by following method when used wet gas flow meter
(pressure 10-3mbar to103 mbar).
Boil-off rate of LN2 at atmosphere pressure in m3 /sec.
0.5 litter = 0.5x 10-3 m3 volumes displaced.
secintakenTime
m10x0.5 3-3

5. Procedure for evaluation of mass flow rate of air
Pressure P= ρgh
Velocity v= (2gh) 1/2
Mass flow rate ṁ= ρAv
6. Results & discussion
Regenerator is the heart of cryocooler refrigeration system. The performance of the refrigeration system is
mainly depends on effectiveness of regenerator. Thus the development of this experimental setup for evaluating
the effectiveness of regenerator at laboratory level is useful for evaluating the performance of cryocooler.
A steady state method for determining the effectiveness of regenerator is adopted.
Following data for regenerator effectiveness test rig is used.
Matrix materials :SS 316 of 400 mesh size
Phosphorous bronze of 150 mesh size
Cycle Time(In Seconds) :3,4,5,6
Pulse rates :20,15,12,10
Mass Flow Rates(Kg/Hr.) :15,21,26,31
There are 1400 no. of meshes of SS 316 densely packed in one regenerator.
There are 980 no. of meshes of phosphorous bronze are densely packed in one regenerator.
Total 1408 meshes of SS 316 & 80 no. of meshes of 100 mesh size of copper material as flow Straightener
is packed in one regenerator. So there are two regenerators with similar geometry & similar no. of meshes are
used in this experimental setup. This is one set of experimental setup.
Total 970 meshes of phosphorous bronze of 10 no. of 100 mesh size of copper material as flow straighter is
packed in one regenerator. So there are two regenerators with similar geometry & similar no. of meshes are used
in another set of experimental setup.
For temporary joint araldite, m-seal and silicon sealants are used. Feed through with 4 connections is used
for prevention of leakage from PT 100 sensor wire’s connections. Soldering is done to the wires for leak
prevention. The PT 100 sensors are connected to the two ends of the regenerator. The other end of the sensor
wire is connected to indicator.
The results of the experimental investigation are shown in below tables & graphs. Fig. 4 and 8 shows that as
mass flow rate increases the boil off rate is also increases. Fig. 5 and 9 shows that as mass flow rate increases
the effectiveness is decreases.

Table 1 Readings of first set of regenerator having 150 mesh size phosphorous bronze material
Cycle
Time
Pulse
Rate
Pressure
Warm
End
Temp.
Tw
Cold
End
Temp.
tc
Temp.
Diff.
mass
flow
rate
Boil off
rate Q
Ineffectiveness e effectiveness є
Sec. Pa ⁰C ⁰C ∆t Kg/Hr. Kg./Hr.
3 20 1 x 105
26.5 7.1 19.4 15 5.26 0.018 0.982
2 x 105
-2.0 -15.7 13.7 21 5.49 0.025 0.975
3 x 105
-26.7 -37.4 10.7 26 5.88 0.027 0.973
4 x 105
-81.9 -89.2 7.3 31 6.28 0.030 0.970
4 15 1 x 105
24.5 6.1 18.4 15 5.29 0.019 0.981
2 x 105
-10.2 -23.2 13.0 21 5.78 0.021 0.979
3 x 105
-35.8 -46.5 10.7 26 6.47 0.023 0.977
4 x 105
-72.8 -82.0 9.2 31 6.86 0.024 0.976
5 12 1 x 105
26.1 7.9 18.2 15 5.49 0.020 0.980
2 x 105
-8.2 -20.8 12.6 21 5.88 0.022 0.978
3 x 105
-32.5 -43.2 10.7 26 6.47 0.023 0.977
4 x 105
-83.8 -92.8 9.0 31 7.06 0.025 0.975
6 10 1 x 105
23.1 5.2 17.9 15 5.69 0.021 0.979
2 x 105
-13.0 -25.9 12.9 21 6.08 0.024 0.976
3 x 105
-45.8 -54.3 8.8 26 6.28 0.028 0.972
4 x 105
-81.2 -88.7 7.5 31 7.06 0.030 0.970
Fig. 4 Mass flow rate Vs. Boil off rate

Fig. 5 Mass flow rate Vs. Effectiveness
Fig. 6 Cycle Time vs. Temperature Difference
Fig. 7 Cycle Time vs. Effectiveness

Fig.6 and 10 shows that as the cycle time increases the temperature difference between hot end and cold
end is decreases at that time the pressure remains constant.
Fig.7 and 11 indicates that for the same pressure and mass flow rate as the cycle time increases the
effectiveness is decreases.
Table 2 shows the readings of SS 316 material with mesh size 400.
Table 2 Readings of second set of regenerator having 400 mesh size of SS 316 material
Cycle
Time
Pulse
Rate
Pressure
Warm
End
Temp.
tw
Cold
End
Temp.
Tc
Temp.
Diff.
mass
flow
rate
Boil
off rate
Q
Ineffectiveness
e
effectiveness
є
Sec. Pa ⁰C ⁰C ∆t Kg/Hr Kg./Hr.
3 20 1 x 105
26.0 2.3 23.7 15 5.34 0.015 0.985
2 x 105
-10.2 -25.6 15.4 21 5.88 0.018 0.982
3 x 105
-38.5 -49.4 10.9 26 6.28 0.022 0.978
4 x 105
-84.2 -92.8 8.6 31 6.47 0.024 0.976
4 15 1 x 105
24.5 1.8 22.7 15 5.49 0.016 0.984
2 x 105
-39.5 -54.6 15.1 21 6.08 0.017 0.983
3 x 105
-82.0 -92.8 10.8 26 6.37 0.022 0.978
4 x 105
-92.8 -101.8 9.0 31 6.77 0.024 0.976
5 12 1 x 105
25.0 4.1 20.9 15 5.69 0.018 0.982
2 x 105
-45.0 -59.4 14.4 21 6.08 0.020 0.980
3 x 105
-81.2 -92.3 11.1 26 6.86 0.023 0.977
4 x 105
-92.5 -101.8 9.3 31 7.26 0.025 0.975
6 10 1 x 105
27 6.9 20.1 15 6.08 0.020 0.980
2 x 105
-38 -50.9 12.9 21 6.57 0.024 0.976
3 x 105
-65 -75.0 10.0 26 6.86 0.026 0.974
4 x 105
-80.7 -89.5 8.8 31 7.45 0.027 0.973
Fig. 8 Mass flow rate Vs. Boil off rate

Fig. 9 Mass flow rate Vs. Effectiveness
Fig. 10 Cycle Time vs. Temperature Difference
Fig. 11 Cycle Time vs. Effectiveness

Fig. 12 Results of IIT Bombay with 200 mesh size.
Fig. 12 shows effectiveness against mass flow rate for constant mesh size 200 for work carried out at IIT
Bombay. In this graph 47, 48, 49 and 50 indicates the SWG.
Graph 5, 9 and 12 represents the same parameters for different mesh size 150, 400 and 200. By comparing
these graphs it is observed that results are similar pattern.
Conclusion
 SS 316 with 400 mesh size gives better effectiveness than phosphorous bronze 150 mesh size.
 Ineffectiveness is more in lower mesh size.
 As the cycle time increases the temperature difference is decreases.
 As the mass flow rate increases temperature difference decreases.
 By increasing mass flow rate boil off rate is also increases.
 By increasing mass flow rate effectiveness is decreasing.
 As the cycle time is less the temperature difference between hot end & cold end is more.
 As the mesh size increases the effectiveness of regenerator increases.
 As the opening & closing time is less remaining mass flow rate constantly low then the effectiveness
is more.
Reference
[1] Andrew Lowenstein"High efficiency Liquid- Desiccant regenerator for air conditioning and Industrial drying" Department of
Energy, Princeton, (2006) PP 1-14
[2] I Ruhlich"Investigations on Regenerative heat exchangers" 12thInternational cryocooler conference (2002) PP. 1-13
[3] J. P. Harvey and P. V. Desai” A comparative evaluation of numerical models for cryocooler regenerators" Advancement in
cryogenic engineering (2009) PP 1-12
[4] K. A. Gschneichnar et al. "Low temperature cryocooler Regenerator materials" 12th Int. cryocooler conf. (2002) PP 1-9
[5] E.D. Marquardt” Compact high effectiveness parallel plate heat exchangers"NIST, Boulder Co. (2009) PP. 507-517
[6] F.X.Eder “A regenerator with a iron whisker matrix advances in cryogenic engineering” 23 ( 1978) PP 448-455
[7] Harris, W.S. “Regenerator optimisation for Stirling cycle regenerator (M. S .thesis)”‘Advance in cryogenic engineering Vol-
16(1971) pp 312
[8] Kasani et al“Performance of a now regenerator material in a pulse tube coolar" Adv. cryogenic Engg. (2003) PP. 985-987

[9] Richard A. Lechner”Investigation of regenerator and pulse tube cryogenic coolers”, (May 1971).
[10] N. Nagraja“Investigation of regenerator matrix for cryo refrigerator” Ph. D. Thesis IIT Bombay(1993)
[11] P.A.Rios and J.L Smith Jr.”‘The effect of variable specific heat of the matrix on the performance the regenerator” Advance
in cryogenic Engineering Vol- 13 ,plenum press, New York (1968), pp 566 –573

Experimental investigate to obtain the effectiveness of regenerator using Air.

Related slideshows

More Related Content

What's hot

What's hot (20)

Similar to Experimental investigate to obtain the effectiveness of regenerator using Air.

Similar to Experimental investigate to obtain the effectiveness of regenerator using Air. (20)

Recently uploaded

Recently uploaded (20)

Experimental investigate to obtain the effectiveness of regenerator using Air.