GB2278912A - Internally enhanced heat transfer tube - Google Patents
Internally enhanced heat transfer tube Download PDFInfo
- Publication number
- GB2278912A GB2278912A GB9415628A GB9415628A GB2278912A GB 2278912 A GB2278912 A GB 2278912A GB 9415628 A GB9415628 A GB 9415628A GB 9415628 A GB9415628 A GB 9415628A GB 2278912 A GB2278912 A GB 2278912A
- Authority
- GB
- United Kingdom
- Prior art keywords
- heat transfer
- ratio
- transfer tube
- range
- pitch
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F1/00—Tubular elements; Assemblies of tubular elements
- F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
- F28F1/40—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only inside the tubular element
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
- F28F13/18—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Geometry (AREA)
- Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
Abstract
An internally enhanced heat transfer tube comprising a heat transfer tube (10, figure 1) including an internal surface 12 and having an internal diameter (D) and a plurality of roughness elements 14 disposed on the internal surface of the heat transfer tube, each roughness element having a height (e) and being spaced from adjacent roughness elements by a pitch (P), the ratio of the top width (a) to the base width (b) being within the range .35 </= a/b </= .65, the ratio of the base width (b) to the pitch (P) being within the range .3 </= b/P </= .8, and the side wall slope (s) being defined by tan s = 2e/(b-a). Preferably the ratio of the height (e) to the internal diameter (D) is in the range 0.004 </= e/D </= 0.045 and the ratio of the pitch (p) to the height (e) is in the range 2.5 </= P/e </= 5.0. <IMAGE>
Description
INTERNALLY ENHANCED HEAT TRANSFER TUBE
The present invention is directed to internally enhanced heat transfer tubes, and more particularly, to an arrangement of roughness elements on the internal surface of the heat transfer tube which provides more efficient and economical heat transfer.
It is highly desirable to limit the material content of the heat transfer tube, particularly as the material in the roughness elements increases the cost of the heat transfer tube. On the other hand, the size, shape and spacing of the roughness elements can be optimized to maximize heat transfer efficiency for all types of tubing used in refrigeration systems.
The enhancements, such as roughness elements, on the internal surface of a heat transfer tube are typically formed by deformation of material. Previous internal enhancement arrangements have not optimally maximized heat transfer efficiency while minimizing material content.
For example, U.S. Patents 4,794,983 and 4,880,054 show projected parts having cavities on the inner wall surface of a tubular body. The ratio of the interval (P) between the projected parts and the height (e) of the projected parts must satisfy the equation 10 < P/H < 20.
U.S. Patent 4,402,359 shows pyramid fins formed integrally on the outer surface of a cylindrical ube. The preferred height of the pyramid fins is about .022 inches at 20 threads per inch.
U.S. Patent 3,684,007 shows a smooth, flat surface having a multiplicity of discrete raised sections in the general shape of pyramids.
U.S. Patent 4,216,826 is an example of an external tube surface including thin walled fins of rectangular coss- section which are about .l millimeters thick and about .25 millimeters high.
U.S. Patent 4,245,695 shows the external surface of a heat transfer tube including pyramid like raised sections with a cylindrical shape. In an experimental example tis patent describes a "circular pitch" of 1.41 millimeter and a .75 millimeter height for the raised parts.
U.S. Patent 4,733,698 shows a complex internal groove arrangement which includes projecting portions having a triangular cross-section.
U.S. Patent 4,715,436 shows a row of projections regularly spaced on the inner surface of a heat transfer tube.
Each projection is composed of a smooth curved surface formed by external deformation of the tube walls. The smallest pitch to height ratio shown is 5.6 (Z/E - 2.45/.45). > U.S. Patent 4,330,036 is similar to the '436 patent in showing a number of beads on the internal surface of a heat transfer pipe.
U.S. Patent 4,660,630 and 4,658,892 are examples of internally finned tubes showing spiral grooves separated by continuous ridges.
The invention provides an internally enhanced heat transfer tube comprising:
a heat transfer tube including an internal surface and an internal diameter (D);
a plurality of uniformly spaced roughness elements on the internal surface of the heat transfer tube, each roughness element having a height (e) above said internal surface, a top width (a), a base width (b), and a side wall slope (s) and each roughness element being spaced from the adjacent roughness elements by a pitch (P), the ratio of the top width (a) to the base width (b) being within the range .35 < a/b < .65, the ratio of the base width (b) to the pitch (P) being within the range .3 < b/P < .8, and the side wall slope (s) being defined by tan s = 2e/ (b-a).
Preferably, the ratio of the top width (a) to the base width (b) is approximately equal to .45.
Preferably, the ratio of the base width (b) to the pitch (P) is approximately equal to .67.
Preferably, the ratio of the height (e) to the internal diameter (D) of the tube falls within the range .011 < e/D < .019.
Preferably, the ratio of the pitch (P) to the height (e) falls within the range 2.5 < P/e S .65.
Advantageously, each said roughness element includes a corner which points in the axial direction of the tube.
The invention also includes an internally enhanced heat transfer tube comprising:
a heat transfer tube including an internal surface and an internal diameter (D);
a plurality of spaced roughness elements on the internal surface of the heat transfer tube, each roughness element having a height (e) above said internal surface and the ratio of the height (e) to the internal diameter (D) being within the range .004 < e/D < 0.45; each said roughness element being spaced from the adjacent roughness elements by a pitch (P) such that the ratio of the pitch (P) to the height (e) falls within the range 2.5 < P/e < 5.0; and
each said roughness element having a top width (a), a base width (b), and a side wall slope (s), the ratio of the top width (a) to the base width (b) being within the range .35 < a/b < .65, the ratio of the base width (b) to the pitch (P) being within the range .3 < b/P < .8, and the side wall slope (s) being defined by tan s = 2e/(b-a).
Preferably, each roughness element is uniformly spaced from the adjacent roughness elements.
Preferably, the ratio of the height (e) to the internal diameter (D) falls within the range .011 < e/D < .019, the ratio of the pitch (P) to the height (e) is approximately equal to 3.0, the ratio of the top width (a) to the base width (b) is approximately equal to .45, and the ratio of the base width (b) to the pitch (P) is approximately equal to .67.
The invention also includes an internally enhanced heat transfer tube comprising:
a heat transfer tube including an internal surface and an internal diameter (D);
a plurality of spaced roughness elements on the internal surface of the heat transfer tube, each roughness element having a height (e) above said internal surface and the ratio of the height (e) to the internal diameter (D) of the tube being within the range .004 < e/D < .045, each roughness element having a top width (a), a base width (b), and a side wall slope (s), and each roughness element being spaced from the adjacent roughness elements by a pitch (P), the ratio of the top width (a) to the base width (b) being within the range .35 < a/b < .65, the ratio of the base width (b) to the pitch (P) being within the range .3 S b/P < .8, and the side wall slope being defined by tan s = 2e/(b-a).
Preferably, the ratio of the height (e) to the internal diameter (D) falls within the range .011 < e/D < .019.
Preferably, each roughness element is uniformly spaced from the adjacent roughness elements.
The invention also includes an internally enhanced heat transfer tube comprising:
a heat transfer tube including an internal surface and an internal diameter (D);
a plurality of spaced roughness elements on an internal surface of the heat transfer tube, each roughness element having a height (e) above said internal surface, a top width (a), a base width (b), and a side wall slope (s) and each roughness element being spaced from the adjacent roughness elements by a pitch (P), the ratio of the pitch (P) to the height (e) being within the range 2.5 S P/e < 5.0, the ratio of the top width (a) to the base width (b) being within the range .35 < a/b S .65, the ratio of the base width (b) to the pitch (P) being within the range .3 < b/P < .8, and the side wall slope being defined by tan s = 2e/(b-a).
Preferably, the ratio of the top width (a) to the base width (b) is approximately .45, the ratio of the base width (b) to the pitch (P) is approximately .67, and the ratio of the pitch (P) to the height (e) is approximately 3.0.
Preferably, the ratio of the height (e) to the internal diameter (D) is within the range .011 S e/D S .019.
In order that the invention may be well understood, some embodiments thereof, which are given by way of example only, will now be described with reference to the accompanying drawings, in which:
Figure 1 shows a perspective view of an internally enhanced heat transfer tube;
Figure 2 shows an optimal arrangement on a flat sheet of the roughness elements of the tube of Figure 1;
Figure 3 is an enlarged sectional view of two of the roughness elements of Figure 2;
Figure 4(a) is an empirically determined graph showing the relationship of material savings to relative roughness for a condenser and an evaporator.
Figure 4(b) is an empirically determined graph showing the relationship of material savings to relative roughness for a chiller evaporator and a chiller condenser;
Figure 4(c) is an empirically determined graph showing the relationship of material savings to relative roughness for a chilled water coil; and
Figure 5 is an empirically determined graph showing the optimal relationship of shape to spacing for the roughness elements of Figures 2 and 3.
Figure 1 shows an internally enhanced heat transfer tube 10 such as might be used for heat transfer between two fluids in an evaporator, in a condenser, in a chilled water coil, in a shell and tube evaporator, or in a shell and tube condenser of a refrigeration system. Other heat transfer applications are also contemplated.
The heat transfer tube 10 has a longitudinal axis, an internal diameter D and an internal surface 12. Roughness elements shaped as flat topped pyramids 14 are located on the internal surface 12 to facilitate heat transfer between the internal surface 12 and a heat transfer fluid flowing within the heat transfer tube 10. The size, spacing shape and proportions of the flat topped pyramids 14 in relation to the internal diameter D and to adjacent pyramids 14 determines the relative roughness of the internal surface 12.
The roughness elements 14 are formed by deforming material from the internal surface 12 of the heat transfer tube 10 in such a manner as to leave only the pyramids 14 projecting above the internal surface 12.
The formation of the roughness elements 14 can be accomplished in a number of ways including the processes shown in U.S. Patents 3,861,462; 3,885,622; and 3,902,552, which are herein incorporated by reference. In these processes the roughness elements 14 are formed on a flat sheet such as is shown in
Figure 2 and then rolled into the tube 10 of Figure 1.
The size of the roughness elements 14 relative to the internal diameter D of the heat transfer tube 10 is such that Figures 2 and 3 also represent the internal surface 12 of the heat transfer tube 10.
After formation, as shown in Figure 3, each pyramid 14 projects above the internal surface 12 by a height (e). In a preferred embodiment each roughness element 14 is uniformly spaced from the adjacent roughness elements 14. As shown each roughness element 14 is shaped as a flat topped pyramid. However, the roughness element may be of any shape falling within the relationships described herein.
The height (e) of each roughness element 14 is such that the ratio of the height (e) to the internal diameter D falls within the range .004 c e/D < .045.
The basis for this range can be seen in the graph of material savings versus relative roughness shown in
Figure 4(a), (b) and (c). These graphs show material savings versus relative roughness for a chiller evaporator 16, a chiller condenser 18, a chilled water coil 20, a condenser 22 and an evaporator 24. From this it can be seen that optimal height (e) to internal diameter D ratio for all heat exchanger tubing 10 falls within the range .011 to .019 with specific optimum ratios of .0125 for the evaporator coil, .0125 for the condenser coil, .019 for the chilled water coil, .015 for the shell and tube evaporator coil, and .011 for the shell and tube condenser coil.Material savings represents the saving in heat exchange tubing material for a given heat transfer application relative to a smooth internal heat transfer tubing surface which has the same heat transfer application and the same minimum tube wall thickness so as to provide the same burst pressure.
As shown in Figure 3, the uniform spacing of the pyramids 14 on the internal surface 12 is determined by the pitch P between arbitrary but corresponding points on adjacent pyramids 14. The pitch P is such that the ratio of the pitch P to the height (e) falls within the range 2.5 < P/e < 5.0 with a preferred pitch (P) to height ratio of 3.0.
The shape of the pyramid 14 is also optimized, as shown in the graph of Figure 5, wherein an optimal pyramid top width (a) to base width (b) ratio of 0.45 is optimal within a preferred range of 0.35 to 0.65, and a roughness element base width (b) to pitch (P) ratio of 0.67 is optimal within a preferred range of 0.3 to 0.8. Also, a roughness element side wall slope (s) is uniquely defined by tan s = 2e/(b-a) = 2/[(b/P) (P/e) (1-a/b)] preferably with an optimal side wall slope of approximately 32".
Preferably, one corner 26 of each roughness element 14 points in the axial direction of the tube and in use, the corner 26 preferably points into the flow of the heat transfer fluid as is shown in Figure 2 by arrow F.
What has been described is an internally enhanced heat transfer tube which optimizes heat transfer. It should be recognized that modifications and alterations of the heat transfer tube as described herein are possible. Such modifications include changing the shape of the illustrated flat topped pyramids to other geometrical shapes within the claimed constraints. For example, the uniform spacing described in connection with the described embodiment could be modified to uniform spacing in a single dimension as compared to the two dimensional spacing illustrated in Figure 2. All such modifications and alterations are intended and contemplated to be within the scope of the present invention.
Attention is directed to Application No.
9121228.2 (Publication No. 2253048) from which the present application is divided.
Claims (15)
1. An internally enhanced heat transfer tube comprising:
a heat transfer tube including an internal surface and an internal diameter (D);
a plurality of uniformly spaced roughness elements on the internal surface of the heat transfer tube, each roughness element having a height (e) above said internal surface, a top width (a), a base width (b), and a side wall slope (s) and each roughness element being spaced from the adjacent roughness elements by a pitch (P), the ratio of the top width (a) to the base width (b) being within the range .35 S a/b S .65, the ratio of the base width (b) to the pitch (P) being within the range .3 S b/P S .8, and the side wall slope (s) being defined by tan s = 2e/(b-a).
2. A heat transfer tube as claimed in claim 1, wherein said ratio of the top width (a) to the base width (b) is approximately equal to .45.
3. A heat transfer tube as claimed in claim 1 or 2, wherein said ratio of the base width (b) to the pitch (P) is approximately equal to .67.
4. A heat transfer tube as claimed in claim 1, 2 or 3, wherein the ratio of the height (e) to the internal diameter (D) of the tube falls within the range .011 < e/D S .019.
5. A heat transfer tube as claimed in any one of claims 1 to 4, wherein the ratio of the pitch (P) to the height (e) falls within the range 2.5 S P/e < .65.
6. A heat transfer tube as claimed in any one of the preceding claims, wherein each said roughness element includes a corner which points in the axial direction of the tube.
7. An internally enhanced heat transfer tube comprising:
a heat transfer tube including an internal surface and an internal diameter (D);
a plurality of spaced roughness elements on the internal surface of the heat transfer tube, each roughness element having a height (e) above said internal surface and the ratio of the height (e) to the internal diameter (D) being within the range .004 S e/D S 0.45;
each said roughness element being spaced from the adjacent roughness elements by a pitch (P) such that the ratio of the pitch (P) to the height (e) falls within the range 2.5 < P/e < 5.0; and
each said roughness element having a top width (a), a base width (b), and a side wall slope (s), the ratio of the top width (a) to the base width (b) being within the range .35 S a/b < .65, the ratio of the base width (b) to the pitch (P) being within the range .3 < b/P < .8, and the side wall slope (s) being defined by tan s = 2e/(b-a).
8. A heat transfer tube as claimed in claim 7, wherein each roughness element is uniformly spaced from the adjacent roughness elements.
9. A heat transfer tube as claimed in claim 7 or 8, wherein the ratio of the height (e) to the internal diameter (D) falls within the range .011 < e/D < .019, the ratio of the pitch (P) to the height (e) is approximately equal to 3.0, the ratio of the top width (a) to the base width (b) is approximately equal to .45, and the ratio of the base width (b) to the pitch (P) is approximately equal to .67.
10. An internally enhanced heat transfer tube comprising:
a heat transfer tube including an internal surface and an internal diameter (D);
a plurality of spaced roughness elements on the internal surface of the heat transfer tube, each roughness element having a height (e) above said internal surface and the ratio of the height (e) to the internal diameter (D) of the tube being within the range .004 < e/D < .045, each roughness element having a top width (a), a base width (b), and a side wall slope (s), and each roughness element being spaced from the adjacent roughness elements by a pitch (P), the ratio of the top width (a) to the base width (b) being within the range .35 S a/b < .65, the ratio of the base width (b) to the pitch (P) being within the range .3 S b/P S .8, and the side wall slope being defined by tan s = 2e/(b-a).
11. A heat transfer tube as claimed in claim 10, wherein the ratio of the height (e) to the internal diameter (D) falls within the range .011 S e/D S .019.
12. A heat transfer tube as claimed in claim 10 or 11, wherein each roughness element is uniformly spaced from the adjacent roughness elements.
13. An internally enhanced heat transfer tube comprising:
a heat transfer tube including an internal surface and an internal diameter (D);
a plurality of spaced roughness elements on an internal surface of the heat transfer tube, each roughness element having a height (e) above said internal surface, a top width (a), a base width (b), and a side wall slope (s) and each roughness element being spaced from the adjacent roughness elements by a pitch (P), the ratio of the pitch (P) to the height (e) being within the range 2.5 S P/e < 5.0, the ratio of the top width (a) to the base width (b) being within the range .35 S a/b S .65, the ratio of the base width (b) to the pitch (P) being within the range .3 < b/P < S .8, and the side wall slope being defined by tan s = 2e/(b-a).
14. A heat transfer tube as claimed in claim 13, wherein the ratio of the top width (a) to the base width (b) is approximately .45, the ratio of the base width (b) to the pitch (P) is approximately .67, and the ratio of the pitch (P) to the height (e) is approximately 3.0.
15. A heat transfer tube as claimed in claim 13 or 14, wherein the ratio of the height (e) to the internal diameter (D) is within the range .011 S e/D < .019.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/660,330 US5070937A (en) | 1991-02-21 | 1991-02-21 | Internally enhanced heat transfer tube |
| GB9121228A GB2253048B (en) | 1991-02-21 | 1991-10-04 | Internally enhanced heat transfer tube |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9415628D0 GB9415628D0 (en) | 1994-09-21 |
| GB2278912A true GB2278912A (en) | 1994-12-14 |
| GB2278912B GB2278912B (en) | 1995-09-06 |
Family
ID=26299647
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9415628A Expired - Fee Related GB2278912B (en) | 1991-02-21 | 1991-10-04 | Internally enhanced heat transfer tube |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2278912B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1137905A2 (en) * | 1998-11-02 | 2001-10-04 | Outokumpu Copper Franklin, Inc. | Polyhedral array heat transfer tube |
| ES2591279R1 (en) * | 2015-05-25 | 2016-12-27 | Icube Ingenieria Internacionalizacion E Innovacion S.L. | Improved cooling system for steam generation boilers |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB536213A (en) * | 1940-08-02 | 1941-05-07 | Clarkson Thimble Tube Boiler C | Improvements in and connected with water heaters and steam generators |
| GB1290588A (en) * | 1969-07-02 | 1972-09-27 | ||
| US4658892A (en) * | 1983-12-28 | 1987-04-21 | Hitachi Cable, Ltd. | Heat-transfer tubes with grooved inner surface |
| US4921042A (en) * | 1987-10-21 | 1990-05-01 | Carrier Corporation | High performance heat transfer tube and method of making same |
| US4938282A (en) * | 1988-09-15 | 1990-07-03 | Zohler Steven R | High performance heat transfer tube for heat exchanger |
-
1991
- 1991-10-04 GB GB9415628A patent/GB2278912B/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB536213A (en) * | 1940-08-02 | 1941-05-07 | Clarkson Thimble Tube Boiler C | Improvements in and connected with water heaters and steam generators |
| GB1290588A (en) * | 1969-07-02 | 1972-09-27 | ||
| US4658892A (en) * | 1983-12-28 | 1987-04-21 | Hitachi Cable, Ltd. | Heat-transfer tubes with grooved inner surface |
| US4658892B1 (en) * | 1983-12-28 | 1990-04-17 | Hitachi Cable | |
| US4921042A (en) * | 1987-10-21 | 1990-05-01 | Carrier Corporation | High performance heat transfer tube and method of making same |
| US4938282A (en) * | 1988-09-15 | 1990-07-03 | Zohler Steven R | High performance heat transfer tube for heat exchanger |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1137905A2 (en) * | 1998-11-02 | 2001-10-04 | Outokumpu Copper Franklin, Inc. | Polyhedral array heat transfer tube |
| EP1137905A4 (en) * | 1998-11-02 | 2002-08-21 | Outokumpu Copper Franklin Inc | Polyhedral array heat transfer tube |
| ES2591279R1 (en) * | 2015-05-25 | 2016-12-27 | Icube Ingenieria Internacionalizacion E Innovacion S.L. | Improved cooling system for steam generation boilers |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9415628D0 (en) | 1994-09-21 |
| GB2278912B (en) | 1995-09-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19981004 |