US20110042037A1

US20110042037A1 - Multi tube-fins liquid-air heat exchanger and methods

Info

Publication number: US20110042037A1
Application number: US12/583,474
Authority: US
Inventors: John Yenkai Pun
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-08-20
Filing date: 2009-08-20
Publication date: 2011-02-24

Abstract

A secondary refrigerant fluid is cooled or heated in the operation of a multiple Tube-fins heat exchanger arranged in parallel for fins to conduct heat transfer with air being propelled by a multi-row bank of low profile brushless fans. Fluid is controlled to ascend the bank of tubes in unison rate for high efficiency heat transfer with air. Large temperature differential exists between air and fluid when conditioned fluid travels through the tubes for a relatively short distance. A system of components is so arranged that the fluid flow rate to every heat exchanger is preset and the “on” or “off” operation of any heat exchanger does not affect the flow rate destined for other heat exchangers. Fluid is not transported to a heat exchanger when it is not in operation saving energy. Each heat exchanger is controlled by an integrated thermostat so occupants can set the air conditioning operation individually independent of all other heat exchangers.

Description

BACKGROUND OF INVENTION

The present invention relates to an apparatus and methods that conduct controllable heat exchange between introduced air and very small amount of cold or hot conditioned fluid.
Heat exchanger technology has long existed with two basic heat transfer mechanisms. In one of the most common applications a single long tube is bent back and forth with scores of thin heat conductive fins in layers attached perpendicularly on the folded long tube. In an attempt to increase heat conduction, an aluminum fin is used with punched holes and tiny collars swaged onto the coursing tube perpendicularly. Air is blown through the fin layers effecting heat transfer between air and liquid inside the tubing. Tubing contacts with the fins are small because the tube being inserted perpendicularly to the fin with small temperature contact area is characteristic of this practice. Purpose of this design is obvious in allowing as much heat transfer possible as fluid courses through the long tube. The fact remains that heat transfer rate decreases as well as heat exchange efficiency as the fluid travels through the tube. This is due to temperature of fluid approaching that of air lowing the temperature differential between the two media as it travels. This kind of heat exchanger typifies most present day fluid air heat exchangers.
Some prior arts modify shape of the tube carrying fluid to gain more tube surface in contact with the surrounding medium as exemplified by U.S. Pat. No. 4,995,454. More commonly occurring is the modification of fins and their attachments to the tubes. These prior arts range from bending fins back and forth a short distance with the bent portion touching the circumference of a tube, helical spiral around the tube, modified fin shapes, to fin creating a vortex air flow as exemplified in U.S. Pat. Nos. 5,398,752; 5,738,168; 6,035,927; 6,119,769; 6,167,950; 6,173,763; 6,349,761; 6,932,153; and 7,438,121. One prior art even uses wire substituting for fins as shown in U.S. Pat. No. 6,192,976. Effectiveness of increase in efficiency of heat transfer is questionable because virtually all these prior arts show very small area of contact between the fin and tube for good temperature conduction.
Tube-fins heat exchanger of this invention provides a very large area of heat conduction path between tube and fin especially the very large ratio between the small mass of fluid to surface area of fin at a given length of tube.
The parallel placed short tubes with fins are designed to achieve maximum heat transfer between air and fluid in a short time interval while the fluid is traveling through the short tube taking advantage of heat transfer is at its maximum when the differential of temperature is greatest between air and fluid.
Rows of low profile DC brushless fans are used to provide air flow for intimate efficient heat transfer between the parallel fins. Each row of fans is individually controlled depending on need of certain amount of heat transfer. Low profile of heat exchanger also allows installation of module inside walls.
Heat exchanger is intended for function in every room and space needing air conditioning. Very small tubings (instead of large air ducts) are used in transport of very small amount of heated and cooled fluid to be processed by the heat exchanger; heat leakage during transport is virtually nonexistent with provision similarly used in cryogenic fluid transport with vacuum. Heat transfer can be accomplished with each heat exchanger at destination needing air conditioning without energy waste.
A unique feature of the apparatus places a heat exchanger in every room, allowing temperature setting for each room to be independently accomplished by an occupant with an integrated thermostat. Conditioned fluid for a heat exchanger not in operation is prevented from being transported to the heat exchanger allowing energy savings.
There are other applications for this heat exchanger besides being used for air conditioning. It can used for measurement of heat leakage of a room with provided temperature sensors measuring input and processed conditioned fluid. Heat exchanger can also be used in collecting waste heat.

SUMMARY

The present invention relates to a modular apparatus and methods for efficient controllable and measurable heat exchange between ambient air and small amount of cold or hot conditioned fluid. Contemporary air conditioners conduct heat exchange between air in a building and refrigerant operating with a single heat exchanger in one locale. Conditioned air must be distributed by an air duct system to various rooms and spaces requiring air conditioning. Air ducts carrying large volume of air consume space, are expensive in components, cost a high amount in installation labor, and waste over 20% electrical energy from heat leakage (experimental conclusion published at Berkeley Lawrence National Laboratory). Output of conditioned air is fixed in a traditional system for delivery to all the rooms or spaces. Shutting conditioned air off to any given room, air destined for that room is distributed to the rest of the system. There is no energy savings by shutting off air to one or more room(s).
Air is a poor conductor. The intermolecular distance is very large so heat (molecular vibration) takes time in transmitting from one molecule to another. Surface radiating heat also takes time to transmit the heat to air molecules. Fluid like water with far closer intermolecular distance transmits heat 24 times more efficiently than air. This also means that heat can be transferred much faster between water and a hot or cold metallic surface besides being transmitted much faster between molecules. Even more important is that water carries 3,716 times more heat than air; only small amount of conditioned fluid needs be transported to each room or space requiring air conditioning instead of very large air ducts carrying large air volume. If we were to substitute a very small tube in the order of ⅛ or ¼% inch ID carrying hot or cold fluid instead of 6×6 inch or larger air ducts to various rooms or spaces, we can use a much better method of insulating heat loss or gain that is far less expensive and endowed with significant conservation of building space besides energy. Heat exchange between fluid and air occurs in a room or space in this invention. Besides the above mentioned advantages, this fluid to air and vise versa heat transfer at destination of usage has far more advantageous features.
Each room's operation of air conditioning can be individually and independently set and controlled by the occupant. People have different temperature preferences even between husband and wife, and this feature is much sought. No conditioned fluid will be processed in an unoccupied room so energy designated for that room can be saved in the operation of the compressor-condenser-evaporator.
The invention of the Tube-fins heat exchanger is also essential in contributing energy and economic savings compared to conventional central air conditioning systems. Virtually all Tube-fins type heat exchangers being used in conditioning consist of a single long tube bent back and forth with fins attached mechanically perpendicular to the tube. The purpose is to conduct heat transfer through the entire length of the long tube to extract or absorb as much heat from fluid flowing through the tube as possible with air flow over the fins. What is not considered is that heat transfer rate is the greatest as fluid first flows through the tube due to largest temperature differential between fluid in tube and air. The tube temperature differential as well as heat transfer efficiency is continuously lowered as fluid travels through the long tube.
Since fluid like water carries 3,716 more heat than air, only a very small amount of fluid per unit time is needed to cool or heat a room or space. A heat exchanger having very high heat transfer efficiency is needed to conduct heat transfer between this small volume fluid and air. Instead of using a single tube, we use many very small tubes so each tube carries only a very small amount of conditioned fluid. Each tube is soldered along its length into a groove formed on a strip of thin metal fin on half its diameter. This method insures the fin making significant thermo-contact with the fluid carrying tube. Assuming we have many of these tubes one foot long and the fins are 1 inch wide by 11 inches long we can fit 47 tubes arranged in parallel in a 12 inch wide area. One foot long ⅛ inch diameter small copper tubing with tube ID 0.087 in is commonly available. Eleven inches long and 1 inch wide with 0.004 inch thick copper sheeting strips are used for fins. In a 12 inch wide area the fins possess 1034 in²or 7.18 square feet of surface area for heat transfer. Heat transfer capability of this heat exchanger is more than enough for a large room. With an electronically controlled pump set at 250 ml fluid being pumped to the exchanger per minute, fluid fills the bank of parallel tubes 4.59 times per minute. Tests have been conducted within these parameters and found heat transfer rate to be very satisfactory. If % diameter tube is used or more ⅛ inch tubes are used air conditioning in a much larger room can be accomplished with a larger size heat exchanger module.
This invention is only interested in conducting heat transfer when the temperature differential between air and fluid is at or near maximum to gain the highest efficiency. It does not matter what temperature the processed fluid has returning to the reservoir to be cooled or heated again. If the temperature of the returning fluid happens to be not overly different from the fluid temperature setting less energy will be used and vise versa.
A vacuum assisted fluid transport system developed to transport small amount of conditioned fluid without noticeable heat leakage is under preparation for a separate patent application. System energy savings is also the center focus. Traditional air ducts have many joints and are not sealed against air leaks. A large amount of insulation material is needed due to the thin material (usually thin metal sheet) that comprises the air ducts; occupation of a large amount of space is also required. ASHRAE (American Society of Heating Air conditioning Engineers), a body that makes recommendations for the air conditioning trade recommends R6 insulation on air ducts due to the final large sizes of insulated air ducts that is hardly adequate for stopping significant amount of heat leakage and still on the average wastes over 20% energy. A majority of existing air ducts in air conditioned buildings do not even meet these inadequate ASHRAE criteria. The other conventional air conditioning method, the split system, has a similar problem using long small tubing to conduct refrigerant with poor or no insulation to prevent heat leakage. This problem can be acute because the surface (of the small tube) to fluid mass ratio is very large; heat transfer rate between air and fluid will also be large. However, small tubing can also be a good thing; insulation can be accomplished with low expense and energy consumption. Vacuum is used for insulation in transport of cryogenic fluid very effectively. Without air there is no heat conduction so vacuum is a good insulator. All needed is to place the fluid transport tube inside another tube and pump the air out. In order to insulate the air conditioning system's components effectively, the invention uses vacuum insulating reservoir and other components besides fluid transport tubes to prevent heat leakage and conserve energy use.
In support of the Tube-fins heat exchanger, a unique method is used to allow presetting flow rate to any heat exchanger that is larger, smaller, or located on a different floor. Every heat exchanger can be turned “on” or “off” and temperature of operation set independently in every room and space; provision is also made so that activities of any number of heat exchangers in operation do not affect the flow rates preset for the remaining heat exchangers. Energy is saved when any number of heat exchangers are not in operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated and form a part of this specification, illustrate embodiments of the invention and together with the descriptions, serve to explain the principles of the invention.

FIG. 1 is a side section view of the Tube-fins heat exchanger showing a tube-fin and direction of secondary refrigerant travel and its connections to refrigerant input and output tubes. The drawing also displays 3 rows of DC brushless muffin fans that blow room air through the Tube-fins heat exchanger and return the air to the room through an air grill.

FIG. 2 is an enlarged view of how air from a room or space is transported by fan(s) through the parallel openings of bank of tube-fins to achieve heat transfer.

FIG. 2 a is a detailed drawing of how a tube is soldered to a stamped channel of a fin.

FIG. 3 is a front view of the Tube-fins heat exchanger FIG. 4 displays how a tube is fitted to the stamped longitudinal slot of the fan.

FIG. 5 shows a frontal view of a Tube-fins heat exchanger module and relationships of tubing connections.

FIG. 6 is a drawing of a wall inside mount module version with narrow profile.

FIG. 7 is a wall mounted Tube-fins heat exchanger module with control positions.

FIG. 8 is a diagram of system operating the heat exchangers allowing each heat exchanger to receive secondary refrigerant independently without changing other heat exchangers' conditioned fluid flow.

FIG. 9 is a perspective view of a motorized recirculation of fluid method through the fins of the evaporator(s).

FIG. 10 is the reservoir inside top view of FIG. 9 showing fluid travel pattern during recirculation.

FIG. 11 is a side view of a dehumidifier module in line with a heat exchanger showing fresh air intake and air travel path.

REFERENCE NUMERALS IN DRAWINGS

- 1. Small diameter copper tubing
- 2. Thin copper fin
- 3. Input copper tubing that connects all small copper tubes at one end
- 4. Short interconnecting copper tube between tubes 3 and 8
- 5. DC brushless muffin fan
- 6. Output copper tube that connects all the tubes at output end
- 7. Input air to the Tube-fins heat exchanger
- 8. Output air to room or space after heat transfer
- 9. Diffuser
- 9 a. Wall board at back of heat exchanger
- 9 b. Outer wall board surface in room
- 10. Temperature thermostat
- 11. Optional relative humidity controller
- 12. Infrared sensor for remote control
- 13. Room air intake grill
- 14. Dehumidifier module
- 15. Air compressor
- 16. Hose transporting compressed air
- 17. Compressed air operated volumetric diaphragm pump
- 18. Secondary refrigerant plenum
- 19. Secondary reservoir containing evaporator(s) and immersed heater(s)
- 20. Fluid plenum collecting secondary refrigerant from valve(s) 19
- 21. Bank of normally open solenoid valves
- 22. Connecting tube(s) from 21 to 23
- 23. Bank of manual adjusting valves
- 23 a. Individual manual operating valves(s)
- 24. Tube(s) connecting 23 and 20
- 25. Bank of normally closed solenoid valve(s)
- 26. Motorized cylinder with paddles for fluid circulation
- 27. Secondary refrigerant
- 28. Evaporator(s)
- 29. Immersed heater
- 30. Direction(s) of travel of circulating fluid
- 31. Direction(s) of travel of returning fluid to the circulator
- 32. Tube-fins heat exchanger
- 33. Dehumidifier
- 34. Fresh air intake

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
As described above, the present invention provides an apparatus and methods for fluid and heat exchange in the application of air conditioning of rooms and spaces in structures or dwellings. More particularly, the apparatus distributes small amount of conditioned (hot or cold) fluid into large number of small tubes each attached lengthwise with thin metal fins and oriented in the same direction FIG. 1, FIG. 2, FIG. 3 and FIG. 4; 1, 2 (47 tubes in a square foot wide area as an example) with the amount of fluid travelling as uniformly as possible from one end to the other end of tubes for conduction of heat transfer with air within a room or space where the heat exchanger is located. The tube is soldered onto a longitudinal groove formed in the fin FIG. 4; 1 and 2. The fin has good temperature conduction with half the diameter of the tube soldered along its entire length. Thin profile brushless DC fans (9 arranged in three rows within a square foot) FIG. 1, FIG. 5, and FIG. 6; 5 mounted on one side of the of tube bank suck in room air and blow the air through the bank of tubes with fins carrying out heat transfer and returning the conditioned air to the room 7 and 8. Processed fluid FIGS. 1 and 6; 6 is returned to a reservoir FIG. 8; 19 that contains an evaporator and submersible electric resistance heaters for reheating or re-cooling processed fluid.
In one embodiment, this invention relates to air conditioning fluid that is cooled or heated instead of air as in traditional systems. Water, for instance, holds 3,716 times more heat that equal volume of air. Large air ducts in central air conditioning can be replaced by small tubes FIG. 8 22 a which transport conditioned fluid to rooms or spaces needing air conditioning supplying heat exchangers for heat transfer with room air. Small tubes are easier to insulate from heat leaks that waste electrical energy over 20% for a large air duct system in transporting conditioned air. In our systems, a large number of rooms and spaces are air conditioned by an equal number of heat exchangers supplied with their own thermostats. This invention differs from traditional air conditioner's single thermostat control for the whole system.
Moreover, each heat exchanger can be turned “on” or “off” independently with its own thermostat FIG. 7; 10 and 12 without affecting others' operations. This invention includes another embodiment that, regardless how many heat exchangers are in operating mode, the conditioned fluid flow rate and pressure remain constant going to every heat exchanger. This operational feature is controlled by novel use of matching solenoid valves combined with manual set valve for definitive flow control FIG. 8; 21, 23, 23 a and 25. One set is incorporated with each heat exchanger so desired amount of conditioned fluid flow is predetermined and preset FIG. 8; 25 and 23 a. The other set is located immediately after the volumetric pump, and its flow is immediately returned to the reservoir FIG. 8′ 21 and 23. The setting of the flow matches that of a heat exchanger. In an “off” mode of a particular heat exchanger, the solenoid valve will be shut. The matching solenoid valve and manual flow valve for that particular heat exchanger will be open returning fluid to the reservoir. When this heat exchanger is turned “on”, conditioned fluid flows into the heat exchanger for conduction of heat transfer; the corresponding solenoid valve by the pump will be shut “off” preventing conditioned fluid flowing back to the reservoir. This novel arrangement allows conditioned fluid flowing to all other heat exchangers to remain the same.
Another significance of the above arrangement is clear; if a heat exchanger is not turned “on”, conditioned fluid designated for that particular heat exchanger is not transported. No heat leakage occurs when the conditioned fluid has to travel such a short distance back to the reservoir. Energy is only expended when a heat exchanger is in operation. Fluid returning to reservoir at the same or near the temperature as fluid inside reservoir does not use additional energy in cooling or heating. Energy savings due to this feature can be significant.
Computer control and sensors integrated with the system, especially those associated with the Tube-fins heat exchanger, offer automated air conditioning temperature setting on a room to room basis that not only saves energy but provides user comfort previously unattainable. Traditional air conditioners' cooling and heating is a simple “on” or “off” operation without gradation control. Once the set temperature from a single thermostat for rooms and spaces is reached, the air conditioner is turned “off”. Depending on the manufacturer, the air conditioner is turned back “on” when the single thermostat measures the temperature to be so many degrees in deviation from preset value. It is not uncommon that one or more rooms have temperatures far different from that measured by a single thermostat in one location causing occupant discomfort and waste of energy.
Rooms of a house have different orientations to the sun, exposures to wind, or lack thereof. Insulation of walls, and number and sizes of windows also play prominent roles in degree and rate of heat leakage. None of these important factors are taken into consideration by existing manufacturers.
Fresh air intake control previously unavailable in domestic air conditioners is included in this invention (FIG. 11). This feature is incorporated especially well into to the wall mounted heat exchangers. Since our Tube-fins heat exchanger is designed to fit into walls constructed with 2 by 4 lumber, and most rooms in a house have one wall facing outside, it is logical to incorporate such an important part of air conditioning function as incorporating outside air with heat exchanger of this invention and dehumidifier (in another invention). Virtually all building codes in US require commercial installations have fresh air intake of 10%. Newer homes have far better insulation than older ones in eliminating air leaks. It is obvious the advancement of insulation methods and materials contribute to build up of carbon dioxide in a house. Dilution of inside air with outdoor air appears to be the simplest economical solution to counter the carbon dioxide problem. This invention again utilizes the basic heat exchanger (or an inline dehumidifier of another invention) for operation of an adjustable air intake to obtain desirable amount of outside air to be incorporated with inside air of that room housing the heat exchanger. Two types of adjusting devices will be used since they can be controlled electronically via a computer and a remote. A screw drive with a stepping motor is one and a rotation device similar to a model airplane control is the other. A remote control can be used to set percentage of fresh air needed, and the computer drives these electronically controlled devices to open or close the vent to the outdoors to preset amount.
FIG. 8 and FIG. 10 depict an optional design for a reservoir 19 with a built-in fluid circulation through the heating 29 (immersed electrical resistance heaters) and cooling 28 (evaporator) components. The stirrer is of paddled and slotted cylindrical construction and is motorized 26. Rotating paddles propel the fluid outward from the stirrer to conduct heat transfer with the evaporator or heating elements 30. Fluid inside the rotating stirrer exits the slots to replace the moving fluid. Fluid 31 is also returned through the bottom of the stirrer to replace fluid exiting the slots.

Claims

1. An apparatus for using cooled or heated fluid in a closed loop system conducting heat transfer with air as heat exchanger for air conditioning and refrigeration comprising: means for controlled fluid flow rate shared by many tubes and ascending the tubes in unison for a short distance conducting heat transfer with high temperature differential between fluid and air; half diameter of the tubes are soldered onto a groove formed longitudinally on the fin to insure maximum heat transfer between tube and fin, a large number of these tube fins are arranged in parallel close together so air can conduct heat transfer intimately with fins, and rows of fans propel air through the spaces between fins for heat transfer.

2. The apparatus as in claim 1, wherein another fluid input tube with multiple short tubes is connected to the primary input tube to insure fluid is traveling through all tubes at uniform rate.

3. The apparatus as in claim 1, wherein the apparatus is installed in every room and space needing air conditioning, and the heat exchanger's operation is controlled by occupant independently from other heat exchangers in an air conditioning system.

4. The apparatus is in claim 1, wherein each heat exchanger is equipped with thermostat and optional relativity humidity control.

5. The apparatus as in claim 1, wherein a heat exchanger can be larger or smaller modules that fit needs of most size rooms.

6. The apparatus as in claim 5 that each heat exchanger is equipped with manual valve for setting conditioned fluid flow rate to match the module size in function.

7. The apparatus as claim 1 wherein the inclusion of temperature sensors monitor temperature of input conditioned fluid and temperature of processed fluid for heat exchanger operation.

8. The apparatus as in claim 7 wherein heat leakage of a room can be monitored by the difference of temperatures of input and output fluid to the heat exchanger at the same time keeping the room temperature constant.

9. The apparatus as claim 1 wherein heat exchanger can be used for reclaiming waste heat to for reuse.

10. A supporting system that includes air pressure generator, air operated diaphragm pump, air storage tank(s), normally closed solenoid valves, normally open solenoid valves, manual valve and sensor/regulator for air pressure to operate in conjunction with Tube-fins heat exchangers that offer functions that are previously unattainable by prior arts.

11. System as in claim 10 wherein air pressure generator and air tanks are used due to the need for a non-corrosive positive displacement diaphragm pump that is in operation with compressed air.

12. System as in claim 11 wherein a positive displacement pump is essential in delivering a pre-set rate of fluid to each heat exchanger without change or its output is not influenced by operation of heat exchangers.

13. A system as in claim 10 wherein each heat exchanger can have required rate of conditioned fluid being supplied pre-set for its size and need.