A thermosyphon liquid-to-air heat exchanger developed for use in heating systems in residential single family dwellings and small commercial applications is described. The cabinet design, rationale for the horizontal positioning of the exchanger, and design of the shut-off valve are discussed. The performance of the heating module is given in tabular form

Hankins, J. D.

English

NASA Technical Reports Server

  
 
 
N O T I C E 
 
THIS DOCUMENT HAS BEEN REPRODUCED FROM 
MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT 
CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED 
IN THE INTEREST OF MAKING AVAILABLE AS MUCH 
INFORMATION AS POSSIBLE 
https://ntrs.nasa.gov/search.jsp?R=19800006241 2020-03-21T20:37:23+00:00Z
DOE /NASA TECHN I CAL
MEMORANDUM
DOE/ NASA TPA-78245
DEVELOPMENT, TESTING AND CERTIFICATION OF THE
SIGMA RESEARCH, MAXI-THERM S-101 THERMOSYPHON
HEAT EXCHANGER -- FINAL REPORT
By James D. Hankins
Solar Energy Applications Projects
George C. Marshall Space Flight Center, Alabama 35812
October 1979
For the U. S. Department of Energy
(NASA-TM-78245)
CERTIF ICATICy pF 
CF.V ELCP"+ FNT, T FSTING ANC
THE SIGMA RES FAPCH,
	
N80-14499MAXI-THFR4-S-101 THERMCSYEHCN
 yFFinal Report (NAS4)19
	
AT EXC HANGERF
HC A02/MF A01
Unc1CSCL 10A G3/44 46457
t`7
4 63
U.S. Department of Energy
^r
Solar Energy
111
LIST OF ILLUSTRATIONS
Figure Title Page
1. Top view of damper and heat exchanger ................ 3
2. Interior view with heat ex. '-• roger removed ............. 4
3. Basic design of a vertical thermosyphon heat
exchanger for use with liquid thermal storage
tanks .................................................. 5
4. Basic design of a horizontal thermosyphon heat
exchanger for use with liquid thermal storage
tanks ................................................... 6
5. Horizontal thermosyphon with parallel flow circuits
and horizontal thermosyphon with parallel-series
flowcircuits	 ........................................... 7
6. Conceptual view of prototype Maxi-Therm 5-101
with	 cabinet
	
installed	 .................................. 8
7. Passive control air shut-off damper for horizontal
thermosyphon	 heat	 exchanger	 .......................... 11
8. Maxi-Therm S-101 heating performance	 ................. 12
9. Minimum performance characteristics of Maxi-The 	 i
model5-101	 ............................................ 13
iv
TECHNICAL MEMORANDUM
DEVELOPMENT, TESTING AND CERTIFICATION OF THE SIGMA
RESEARCH, MAXI-THERM S-101 THERMOSYPHON
HEAT EXCHANGER - FINAL REPORT
PROGRAM BACKGROUND AND GOALS
Before dealing with the specific aspects of the Sigma Research
exchanger, a few background statements are pertinent. The problems
of energy availability and increasing costs have led to a major national
effort to develop alternate energy soarces. One such source is the
energy in solar radiation which can be used for heating and cooling
buildings, domestic hot water, and other applications. The National
-nergy Policy, as established in the Solar Heating and Coo l. - ..g Demon-
stration Act of 1974 (PL93-409) , provided for the demonstration within
a 3-year period of the practical use of solar heating technology, and
demonstration within a 5-year period of the practical use of combined
heating and cooling technology. Responsibility for implementing the
Demonstration Act was given to the Energy Research and Development
Administration (now the Department of Energy). The National Aero-
nautics and Space Administration (NASA), George C. Marshall Space
Flight Center (MSFC) manages a large part of this work.
PRODUCT DEVELOPMENT CONTRACT
The purpose of this contract was to provide Sigma Research with
funds to do additional development, design and testing on their existing
passive Thermosyphon solar heating module (with supplementary heating)
to make a marketable product and for the procurement of the developed
subsystem. Each subsystem consists of one heating module (passive
heat exchanger) and one submersible electric water heating element.
During the prodilet uevelopment effort, the contractor was required
to:
1) Meet the pertinent parts of the Interim Performance Criteria.
2) Meet the Subsystem Performance Specification
3) Conduct tests and provide test data/analysis to verify that
hardware meets the Subsystem Performance Specification
4)	 Provide drawings find specifications
1
in sufficient detail to define
the configuration and to ensure manufacturing repeatability
5) Provide installation, operation and maintenance manuals(s)
6) Provide subsystem and/or component hardware certification by
an independent test laboratory (such as, Underwriters Laboratory and
American Gas Association) to meet nationally recognized standards and
codes (such as, American Society of Heating, Refrigeration and Air
Conditioning Engineers; American Society of Mechanical Engineers;
American National Standards Institute and American Refrigeration
Institute) .
DESCR I PTI ON
The Maxi-Therm S-101 is a thermosyphon heating module utilizing
a horizontal liquid-to-air heat exchanger, a Dayton direct drive blower
and an automatic air shut-off damper. Figure 1 shows a view of the
damper (air shut-off valve) and the heat exchanger while Figure 2 shows
the complete module with heat exchanger removed.
Heat Exchanger
The performance of the Maxi-Therm is determined primarily by the
effective performance of the liquid to air heat exchange element. For
this reason, a great portion of the activity was spent on the further
development of the design of this element.
During the phases of development, the exchanger module was
reoriented to a horizontal rather than a vertical position. The rationale
for the vertical to horizontal switch was better performance. For vertical
thermosyphons operating in the heating mode (Fig. 3), water enters at
the top, flows vertically downward through the heat transfer elements,
and exits at the bottom of the exchanger prior to reentry into the
thermal storage tank. During its downward movement, the water gives
up heat to the air, thus falling in temperature and rising in density.
The pressure which drives the water flow in the system then originates
due to the density differential existing between the water in the heat
transfer elements of the exchanger and the storage tank.
In a horizontal thermosyphon (Fig. 4). a simewhat different driving
pressure expression is realized since the rise in density of the water
occurs during flow in a horizontal plane. Before entering the vertically
oriented outlet piping, which connects the exchanger outlet to the bottom
of the tank, the water has already reached its maximum density. The
horizontal possesses a greater driving pressure differential and, con-
y , sequently  a higher mass flow rate is realized.
2
OA
Rim
Figure 1. Top view Of (Infilper :111d heart exclimiger.
OPIGCOV1 ,71 	 • ".,.(
of P00 14 -,;- :
Fil urr
	 Interior %-ie%v with lWAt
	 1*0111 VO(l.
TUBESHEET WARM WATER TO
STORAGE TANK
PLENUM
INLET PIPING
HOT WATER FROM
TUBE SHEET-
	 STORAGE TANK
HEAT TRANSFER
ELEMENTS
WARM AIR
	
—
	
^ 	 COOL AIRTO ROOM
FROM ROOM
f^
f--
CHARACTERISTIC
HEIGHT "h"
OUTLET PIPING
PLENUM
Figure 3
	
Basic design of it vertical thermosyphon heat exchanger
for use with liquid thermal storage tanks.
Another reason for the position change was the additional advantage
provided by the horizontal exchanger position i. ► relation to the circuiting
of liquid flL. in the heat transfer elements. The vertical unit is con-
strained to use only multiple parallel paths connected to common plenums
tit each end. The horizontal unit may utilize totally parallel or parallel-
series circuiting. In figure 5 it 	 is shown between the now
in it total paral l el system and in one type of parallel-series arrangement.
In the ehange -over from vertical to horizontal, special attention had
to be paid to the inlet and outlet piping. The reason for the special
5
WARM AIR TO ROOM
TUSE &MEET 1
	
PLENUM
INLET PIPING
NOT WATER
^- FROM
STORAGE TANK
I	 I
COOL AIR FROM ROOM
VERTICAL PORTION
Of OUTLET PIPING
WARM WATER
TO STORAGE TANK
HORIZONTAL PORTION
OF OUTLET PIPING
CHARACTERISTIC
HEIGHT 91'
Figure 4. Basic design of a horizontal thermosyphon heat exchanger
for use with liquid thermal storage tanks.
attention was that the primary heat transfer elements in the horizontal
position do not form the vertical link necessary between tank exit and
inlet.
In order to minimize pressure drop in piping and thus increase the
mass flow rate, it was ad • rantageous to increase pipe diameter and
decrease pipe length. However, it was further determined that a
decrease in outlet pipe lenirth, in the case of the vertical portion, is
not desirable since it is this length that determines the thermosyphon
driving pressure. It was also determined that it decrease in the hori-
zontal position is likewise undesirable, since sufficient distance must be
provided between the Maxi-Therm unit and the storage tank to permit
the installation of pipe couplings. Therefore, it was determined that the
diameter change is the best variable to use if a lower system pressure
drop is required. A change in this variable also produces the most
effect on piping pressure loss.
6
HEADER
PLENUM	 ,TUBE SHEET	 TUBE SHEET
	 PLENUM
_11111111111111 11 III III Jill I
	
--	
^,
	
lillllll
	 III,	 \
--	 ^- —
^`.	 II	 III^II^,	 ^
HORIZONTAL THERMOSYPHON WITH PARALLEL FLOW CIRCUITS
1800 RETURN BI
HEADER
HORIZONTAL THERMOSYPHON WITH PARALLEL-SERIES FLOW CIRCUITS
Figure 5. Horizontal t tic rmosyplion with parallel flow circuits and
horizontal thermosyphon with parallel-series flow circuits.
The final design of the heat exchanger module was completed in
March of 1977. The final element is a 56-tube, parallel-series flow
arrangement with four tubes in a series. This module is commercially
available from suppliers.
Cabinet
The primary purpose of the cabinetry for the Maxi-Therm is to
provide ma-,dmum satisfaction to the potential market. The I11axi-Therm
cabinet was designed to provide a pleasing appearance, easy module main-
tenance, low cost production, and simple assembly !ind disassembly.
I
	
	
In Figure 6, a conceptual view is shown of the Maxi-Therm S-101
module with the exterior shell in place. As noted in Figure C, the shell
consist of basically four sections, labeled A, B, C. and D. By designing
the shell in this manner, a number of advantageous features were made
possible.
7
MEATExCMANaER
PANEL D
WATER INLET TUBE
WATER OUTLET TUBE
PANE L C
PANEL A
REMOVAILE AIR FILTER
ACCESS DOOR
Figure 6. Conceptual view of prototype Maxi-Therm S-101
with cabinet installed.
First, in the production of the shell, the formation of complicated
or intricate bends is not required, thus permitting the components to be
manufactured on a normal brake and shear. In addition, the use of
Panels A and C to form they finished corners permits Panels 13 and D to
have flat, as-produced edges and further decreases the number of critical
dimensions required in their production.	 y
Combining the function of the cabinet with other requirements is
also possible with this design. As shown in Figure 6, a portion of Panel
B acts as the air inlet and the Slter holder is attached to its backside.
8
Access to this filter is provided by the indici,ted removable cover on
tnel C. The cabinet as a whole further acts as both the inlet and
outlet air plenums, with a horizontal sheet steel divider separating the
two sections. The seal between the inlet and outlet plenum is provided
by foam rubber strips which are bonded to horizontal frame stiffeners
positioned directly below the divider and extending the entire circum-
ference of the unit.
Originally, the entire electrical component package was considered
for mounting within the shell. This design, however, wits modified to
position the electrical components within a separate electrical box attached
to the outside of Panel D. Primarily. this wits done to eliminate possible
^onflicts with local electrical codes concerning the danger of 115 Vac
junctions in the proximity of it heat exchanger containing water.
Shut-Off Valve
During the early development of a thermosyphon water-to-air heat
exchanger, it became apparent that the unit possessed one particular
trait not usually found in heat exchangers, that being the requirement
for a positive shut-off valve. In normal forced flow exchangers,
cessation of water pump operation is sufficient to halt exchanger opera-
tion. In thermosyphon units, however, the movement of air through the
exchanger and the subsequent decrease in water temperature create the
liquid driving force which increases the liquid circulation. To shut the
device of;, either air movement of liquid circulation must be elimii ated.
Initially, investigations were made into the use of a water-side
shut-off. This type of device, it was found, would require use of an
electric solenoid, a component which added both cost and a potential area
°-or maintenance/repair in the future. In addition. most types considered
required a movable sha ft and settled penetration through some portion of
the transfer system piping. Besides the cost, this represented a poten-
tial area for leakage and additional maintenance. Ac.other consideration
wits the possible effect on transfer system pressure drop that a valve.
even in the full open position, would create and the corresponding effect
that it would have on module thermal performance.
When it wits found that a water-side shut-off would not be
desirable, investigations were commenced to define possible air-side
p hut-off valves. Since tale position of the valve with respect to the
heat exchanger hit, a strong bearing on the design, this was the first
area to be investigated. Consideration was given to two locations during
these studies, one being the outlet ducting and the other, the plenum
area immediately attwve the heal exchanger. Since the outlet ducting will
not be included with the Maxi-Therm unit, the installation of a factory
supplied shut-off' in the outlet ducting would entail additional cost , the
9
homeowner and would not guarantee proper installation. In addition,
insulation would be required on the section of ducting t)etween the
exchanger and shut-off valve to avoid excessi-e heat loss. These draw-
backs were felt to be serious enough to consider the second location,
which is within the outlet plenum. Although this position does require
fitting the valve to a predetermined opening size, thus eliminating
flexibility in sizing, it does eliminate the need for additional insulation
and allows the valve to be installed at the factory.
Following selection of the latter position for the valve location,
attention was next turned to the design of the component. For this
application, it 	 vane damper similar to that shown in Figure 7
appearf to be it good choice. with the method of actuation being the
only area of investigation. Basically, this actuation can be provided by
either it 	 or differential pressure across the damper, such as that
generated by the blower fan. The latter of these two was the preferred
choice, since the cost of it 	 and the associated linkage generally
raises the price by $50 .. $+100. In addition. the passive opening system
does not require maintenance or adjustment after leaving the factory.
The multi-vane damper was selected in March of 1977. The item
was procured front 	 supplier and is commercially available.
PERFORMANCE
The NInxi-Therm S-101 will deliver more and more heat its the inlet
water temperature increases. The air handling fan is rated Ott 1640 cfm,
and is operated by it 	 hp. 6.5 amp full load, 115 Vnc mi..-.)r. This
air flow is delivered at 0.6 in. water static pressure to provide adequate
cur distribution th-oughout the home. The performance of the Maxi-
Therm S-101 heating performance is depicted in Figures 8 and 9.
CONCLUSIONS AND RECOMMENDATIONS
This contract wits successfully completed during October 1977 with
the acceptance, by Marshall Space Flight Center, of three subsystems
which had been inspected, tested and verified to exceed the expected
design performance c^iteria.
No major problems were encountered during the development of the
subsystems, although the heat exchanger position was changed from
vertical to horizontal. and the exchanger tube size, due to economic
factors. was limited to the commercially available maximum.
10
U)
a
ro
U
kU
ro
a^
0
a
0
E
c.
a^
ro
G0N
0
f-/
0
it
d
CL
E
cnb
w
w0
I
Ln
f~
a-+
U
U
:n
ro
a
a
a
a
bD
P4
11
N
x
O
ou
^ ^ J
.r o ^ o 0 0v
c
y
it
7
~ Uv ^
E
,u c.
H w
^ w aN
``^^
W
b a^
v .^
0
r-.
n
H
a^
ILI
t.
.y 1,
N
.r
H ^
a CU
y
E"4	(iy
J ^
O
^Q
v
.-r
rl
iA
1 •r
f10QQ JNIlV
Q
3H
^S E	 25
Ri	 o 0
LL
O
U
Or
N
O.
W
l`
cc
Q
H
WJZ
J
O
C7
r
H ((^^^
W
W
N	 ^ N -i
co	 F.-
M	 N WQ
Z ZW
I^to ¢	 co
O x
W
O 3
LL
O aQ
b
^
00U H oZ^
fu O J
LL^
LL
U. Z
0
O // 0
19
W
H O
c C
a H 1- O
H Q
l-W H U
y
LL V
O U cc	 ti0
M
N a h	 Vz N
z
W
; p
a Z I O
z<
O
F cc J
Q O LL
ao
Cr LL
C7
W Z
CL Y
O
3:
0
9	 U)
O
	
O	 E
	
7	 E
	
_	 C+
{0  Q H
	
^	 I
W
-d	 co
Z
O O
ul
1^ JLLQ ^^
W
	
I	 ^
WU ^
ZW U
	
ac	 y
W V
LL
LL ^
E
	W 	 tti
Q 20
H ^
	
N Q	 >=L
W 
E
	
a	
:1
W E
Or
rn
d
s~
Gtr
M
N N N N co w a cm O co 	 t0 V N O O
	
{w
sjAvm011)
	 indino JNIlV3H
Im
13
The technology for thermosyphon systems is not new. Many of
the early (and late) solar hot water systems use thermosyphon circula-
tion technologies. The origin of the term "thermosyphon" is uncertain,
but the name did appear as early as 1928 in the sales literature of
Deere (John) and Company cooling systems. The Model T Ford is
perhaps the first automobile to use thermosyphon cooling.
Passive thermosyphon systems are inherently less expensive to
operate and maintain than active systems. In the past, many thermo-
syphon solar hot water heating systems were used because electricity or
other conventional energy was not available or too expensive. That same
situation is rapidly approaching again — but on a much larger scale.
Because thermosyphon devices can be designed, and are available, to
conserve energy without imparing performance, they should be considered
for use in many solar heating systems.
The Maxi-Therm S-101 developed during this contract is not yet
available as an off-the-shelf item. Production, other than special
orders, will be determined by market potential and demand. Sigma
Research, Inc., Richland, Washington, Should be contacted for additional
information.
14
REFERENCES
1. Passive Thermosyphon Solar Heating and Cooling Module with
Supplementary Heating (Quarterly Report) DOE/NASA CR 150849,
Contract NAS8-32260, Sigma Research, Incorporated, Richland,
Washington.
2. Installation Package Maxi-Therm 5-101 Heating Module, DOE/NASA
CR 150512, Contract N AS 8- 32'260 , Sigma Research, Incorporated,
Richland. Washington.
3. System Design Package Maxi-Therm S-101 Heating Module, Passive
Heat Exchanger. DOE/NASA CR ,x0516, Contract NAS8-32260,
Signor Research, Incorporated, Richland, Washington.
4. A Passive Thermosyphon Heat Exchanger for Residential Solar
Applications, pages 27-30. Section 9, Volume one, Proceedings of
the 1977 Annual Meeting, Orlando, FL, June 6-10, 1977, American
Section/International Solar Energy Society, Killien, Texas.
Items 1 through 3 may be obtained through the Department of Energy,
Technical Information Center, Post Office Box 62, Oak Ridge. Tennessee
37830, or Marshall Space Flight Center, Alabama. Item 4 may be obtained
from American Section/International Solar Energy Society, Killien, Texas.
15
L_
APPROVAL
DEVELOPMENT, TESTING AND CERTIFICAT!ON OF THE SIGMA
RESEARCH, MAXI-THERM S-101 THERMO SYPHON
HEAT EXCHANGER -- FINAL REPORT
By James D. Hankins
The information in this report has been reviewed for technical content.
Review of am information concerning Department of Defense or nuclear energy
activities or programs has been made by the NISFC Securit y Classification Officer.
This report. in its entirety, has been determined to be unclassified.
WILLIAM A., RORTRSBANK, JR.
Manager. Solar F,nergy Applications Projects


Development, testing and certification of the sigma research, maxi-therm-S-101 thermosyphon heat exchanger

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server