Experimental development of tubseide heat transfer correlations for laminar flow with and without inserts.

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by  Guido, Joseph D.;Marto, P. J.;Memory, Stephen B.

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X. TPITELREI(InMckEjdaNSeTcuAritLyClDamEaMVcaHEonL) OPMENTOF TUBESIDE HEATTRANSFER CORRELATIONS FOR LAMINAR FLOW
rITH AND WITHOUT INSERTS
PERSONALAUTHOR(S)
.
uido, Joseph D.
a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORTffc,Ma.Day) 15. PAGE COUNT
aster'sThesis FROM TO 1992, June 17 177
SUPPLEMENTARY NOTATION: The views expressedin this thesis are those of the author and do not reflect the official policy
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COSATI CODES 18. SUBJECTTERMS (Cans*—onmmmameaawmyandidantttybyblocknumbatj
FIELD GROUP SUB-GROUP Laminar Flow, Tubeside Heat Transfer,TwistedTape and HEATEX Inserts
. ABSTRACT {ContinueonravanaifnacaaaaryandIdantttybybtocknurnbat)
i experimental studyoflaminar flow heat transferofan ethylene glycol/water mixture in anelectrically heated horizontal tube usingwire mesh
EATEX) and twisted tape insertswas investigated. Twelve thermocouples, inserted in the tube wall at four longitudinal locations,enabled a mean inside
perimental heat-transfer coefficient to be accurately measured. A constantwall heat flux boundary condition was placed on the wall bywrapping six 200
flexible heater tapes tightlyaround the tube. The ethylene glycol/water mixture provided acoolant Reynolds number between 200-5000 and a Prandtl
mber between 30-140. Twosmooth inside diameters and a roped tube profile were testedwith and without the inserts. Heat-transfer correlations for
?es without insertswere developed and comparedwith theory for both thermallyand hydrodynamicallydeveloping flow. Correlations were also
veloped for the two types ofinserts. Nusselt numbers for fullydeveloped flowwere found to be a function of Reynolds and Prandtl numbers for the wire
sh insert and a function of tape twist ratio, Reynolds and Prandtl numbers for the twisted tape insert. Heat transfer enhancements ofover 7 for the wire
:sh insert and over 4 for the twisted tape insert at high Reynolds numbers were obtained over the empty tube. By using these correlations in conjunction
th earlierobtained refrigerant condensation data (using the same tubes, inserts,and coolant), more accurate values ofthe outside condensation heat-
nsfer coefficients were obtained.
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EXPERIMENTAL DEVELOPMENT OF TUBESIDE HEAT TRANSFER
CORRELATIONS FOR LAMINAR FLOW WITH AND WITHOUT INSERTS
by
Joseph D. Guido
Lieutenant Commander, United States Navy
B.S.N.E., University of Florida, 1981
Submitted in partial fulfillment of the
requirements for the degree of
MASTER OF SCIENCE MECHANICAL ENGINEERING
from the
NAVAL POSTGRADUATE SCHOOL
September 992
-A
ABSTRACT
An experimental study oflaminar flow heat transfer ofan ethylene glycol/water
mixture in an electrically heated horizontal tube using wire mesh (HEATEX) and
twisted tape insertswas investigated. Twelve thermocouples, inserted in the tube wall
at four longitudinal locations, enabled a mean inside experimental heat-transfer
A
coefficient to be accurately measured. constant wall heat flux boundary condition
W
was placed on the wall by wrappingsix 200 flexible heater tapes tightly around the
tube. The ethylene glycol/water mixture provided a coolant Reynolds number
between 200-5000 and a Prandtl number between 30-140. Two smooth inside
diameters and a roped tube profile were tested with and without the inserts. Heat-
transfer correlations for tubes without inserts were developed and compared with
theory for both thermally and hydrodynamically developing flow. Correlations were
also developed for the two types of inserts. Nusselt numbers for fully developed flow
were found to be a function of Reynolds and Prandtl numbers for the wire mesh
insert and a function of tape twist ratio, Reynolds and Prandtl numbers for the
twisted tape insert. Heat transfer enhancements of over 7 for the wire mesh insert
and over 4 for the twisted tape insert at high Reynolds numbers were obtained over
the empty tube. By using these correlations in conjunction with earlier obtained
refrigerant condensation data (using the same tubes, inserts, and coolant), more
accurate values of the outside condensation heat-transfercoefficientswere obtained.
in
Am
I
TABLE OF CONTENTS
INTRODUCTION
I. 1
BACKGROUND
A. 1
B. REFRIGERANT CONDENSATION RESEARCH AT NPS 2
C. OBJECTIVES 7
LITERATURE SURVEY
n. 8
INTRODUCTION
A. 8
B. LAMINAR FLOW IN CIRCULAR DUCTS 9
1. Boundary Layers and Entrance Lengths 9
a. Hydrodynamic Boundary Layer 9
b. Thermal Boundary Layer 10
2. Fully Developed Flow 12
3. Entry Length Problem 14
a. Thermal Entry Region - Uniform Wall Temperature ... 15
b. Thermal Entry Region - Constant Wall Heat Flux 17
c. Combined Entry Length 17
IV