Condenser Coil Apparatus

Abstract

A refrigerant condenser coil having a fan arranged to draw fresh air through one section of the coil and blow the air through another section of the coil. Preferably the coil is annular in plan outline, and the fan is arranged in the space circumscribed by the annular coil. The circumscribed space can also contain a refrigerant compressor.

Description

BACKGROUND OF THE INVENTION

It is known to provide air conditioning systems of the so-called "split system" character wherein the refrigerant evaporator is located in a furnace duct, and the refrigerant compressor and condenser are remotely located on a cement slab located outside the residence. In such split systems the condenser is cooled by a fan arranged immediately adjacent the coil. Commonly the compressor is located alongside the condenser coil in a common casing.

The present invention seeks to improve the construction of the "split system" condenser-compressor package, particularly by reducing the size and cost of the package, by eliminating certain of the casing components, and by more effectively utilizing the space occupied by the package.

THE DRAWINGS

FIGS. 1, 2 and 3 are schematic representations illustrating the operation of three different condenser fan-coil arrangements;

FIG. 4 is a sectional view taken through a condenser-compressor assembly constructed according to this invention;

FIG. 5 is a sectional view taken on lines 5--5 in FIG. 4;

FIG. 6 is a fragmentary sectional view of a detail used in the FIG. 5 construction;

FIG. 7 is a view of a detail that can be used in of the FIG. 6 detail;

FIG. 8 is a fragmentary view of a corner construction useful as an alternate in the FIG. 5 assembly;

FIG. 9 shows a detail that can be used to mount a venturi panel in the FIG. 4 construction;

FIG. 10 is a schematic representation of a refrigerant coil passage arrangement useful in practice of the invention.

FIGS. 1 - 3

FIG. 1 schematically illustrates a fan-coil arrangement comprising an air duct 10 having a venturi panel 12 in which is located a propeller fan wheel 14 for moving air rightwardly through a plate fin refrigerant coil 16. The coil has two rows of refrigerant tubes 18 extending transversely through plate fins 20, said fins having leading edges 22 and trailing edges 24.

FIG. 2 shows a fan-coil unit very similar to the FIG. 1 unit except that the coil is comprised of two coil sections 16a and 16b. The two coils have twice the number of leading edges and twice the number of trailing edges as compared with FIG. 1; assuming the same volumetric air flow, the FIG. 2 coil arrangement therefore provides a somewhat higher heat transfer capability because the extended (fin) surface temperature does not conduct to cooler tubes within the coil core, normally downstream in a counter flow (air vs. refrigerant) arrangement. Also, the amount of leading fin edge is doubled or tripled (depending on comparison to a comparable 2 or 3 row capacity coil) thus increasing the resultant heat transfer area of the extended surface. The air flow resistance (pressure drop characteristic) is approximately the same for the two units when at actual air temperature; i.e: at normal operating conditions.

FIG. 3 shows a fan-coil arrangement having the same number of refrigerant tubes as the coils in the FIG. 1 and FIG. 2 units. In the FIG. 3 arrangement the coil has one row of tubes, arranged eight tubes per row. The heat transfer capability of the FIG. 3 unit is somewhat less than that of the FIG. 2 unit because of a lesser linear air velocity through the FIG. 3 unit (assuming the same volumetric air flow for each unit).

In further explanation of the above, if we assume that the FIG. 1 coil has a face area of 2 square feet, and that fan 14 provides a linear velocity of 400 feet per minute, then the volumetric air flow through the FIG. 1 unit will be 800 cubic feet per minute. Assuming the same volumetric air flow for the FIG. 2 unit, namely 800 cubic feet per minute, we will have the same linear velocity of 400 feet per minute. However the heat transfer capability of the FIG. 2 unit will be greater because of the single row design, as previously noted. The air flow resistance (pressure-drop characteristic) for the FIG. 1 and FIG. 2 units will be the same.

Assuming the same linear velocity of 400 feet per minute, the FIG. 3 unit will have a volumetric flow requirement twice that of the FIG. 1 or FIG. 2 units, namely 1,600 cubic feet per minute. The higher volumetric flow requirement of the FIG. 3 unit makes less desirable than the FIG. 1 or FIG. 2 units because of the larger duct dimensions and higher noise emission. On an overall basis it is believed that the FIG. 2 unit combines the best characteristics of the three arrangements, i.e., a low volumetric air flow requirement and a high inherent heat transfer capability as previously noted in the FIG. 2 description.

FIGS. 4 and 5

FIG. 4 shows a condenser-compressor package of this invention, comprising a bottom panel 30, a top panel 32, and an intermediate venturi panel 34. Interposed between the bottom panel 30 and venturi panel 34 is a refrigerant condenser coil section 16a of the plate-fin type; another similar coil 16b is interposed between panels 34 and 32.

As shown in FIG. 5 each coil is of square annular configuration in plan outline. The various heat exchange tubes 18 and 18b run transversely through the plate fins 20a and 20b from a vertical inlet header 42(FIG. 5) around the annular circumference of the unit to other headers designated 44 in FIG. 5. It will be appreciated that the tubes 18a and 18b are arranged horizontally one above another, and that the plate fins are arranged vertically in planes generally normal to the sides of the square outline (except at the corners). As seen in FIG. 4, each coil 16a and 16b is provided with six heat exchange tubes arranged in a single row. In practice a greater number of tubes would be provided, depending on the size of the condenser, i.e., condensing requirement.

The space circumscribed by coil sections 16a and 16b is occupied by a fan which comprises a fan motor 42 and a propeller fan wheel 44. As shown in FIG. 4 the fan motor is suspended from a diffuser cone 46 which connects with the top panel 32: the motor could be mounted in a spider carried by venturi panel 34. The propeller fan wheel 44 is disposed within the venturi opening in panel 34 for producing an upflowing air movement through the venturi opening. Therefore, the fan draws outside air inwardly through the lower coil section 16a and blows said air outwardly through the upper coil section 16b. By comparing FIG. 4 with FIG. 2 it will be seen that the two respective arrangements are generally similar to one another in that in both instances the fan wheel is arranged for draw-through action with respect to one of the coils and blow-through action with respect to the other coil. The FIG. 4 arrangement is a practical form of the FIG. 2 schematic representation. The FIG. 4 unit embodies the advantageous operational features of the FIG. 2 unit in a desirably compact package occupying minimum space. Space economy is further achieved in that the zone below the fan wheel 44 is used to contain a conventional refrigerant compressor 48.

COIL MANUFACTURE

Each coil 16a or 16b is initially formed in the flat, using straight heat exchange tubes 18a or 18b threaded through openings in the collars 52(FIG. 6) of the plate fins 20a or 20b. After formation of a suitable tube-plate stack a mandrel is forced through each tube to expand the tube into tight mechanical bonding engagement with the fin collars. Thereafter the headers 42 and 44 are applied to the exposed tube ends, and the fin-tube assembly is bent around arcuate forming dies to achieve the square shape of FIG. 5.

The illustrated assembly includes flanged tube sheets 49 and 51, and intermediate bracket plates 50 between selected ones of the fins as shown in FIG. 6. The tube sheets and bracket plates are positioned on the heat exchanger tubes as part of the fin-tube stack (prior to mandrel expansion of the fins onto the tube collars 52). Thus, when the mandrels are forced through the tubes to expand them into tight bonding relation with the fin collars 52 they also affix the tubes to the tube sheet 49 and 51, and the bracket plates 50.

As shown in FIG. 6, each bracket plate 50 is preformed with a sleeve-like extension 54. After the heat exchange coils are bent into the square annular configuration of FIG. 5, and the components are stacked on one another (as shown in FIG. 4) suitable tie bolts (FIG. 6) can be inserted through the sleeves 54 to tie the assembly together. Suitable nuts 58 can be threaded onto the lower ends of the tie bolts to retain the assembly together. Tube sheets 49 and 51 may be welded together or screwed together at their facing flanges.

FIG. 7

FIG. 7 illustrates an alternate mechanism for securing the two heat exchange coils to the various plates 30, 34 and 32. As shown in FIG. 7, each heat exchange coil can be provided with a bracket 50a having a flange foot portion 53 arranged to lie flat against the respective panel 30, 32 or 34. Suitable welding screws, etc., can be used to secure the bracket to the respective panel. The bracket is secured to the heat exchange coil by the tube-expansion method described in connection with FIG. 6.

FIG. 7 shows one bracket at the lower end of a heat exchange coil 16a, but it will be appreciated that a similar bracket can be located at the upper end of each coil so that each coil can be secured at its upper and lower ends to respective ones of the panels 30, 32 and 34.

AIR VELOCITY

It is desirable that the air velocity across the fins be relatively high in order to achieve a scrubbing action on the fin edges and fin surfaces. With the arrangement of FIG. 4 a given volumetric air flow by fan 44 is accompanied by a relatively high linear velocity because the total air volume is forced through two coils in series with one another. The flow cross-section of each coil is only one-half that of the conventional flow through unit (FIG. 3) so that the linear velocity through each FIG. 4 coil is twice what it would be if the air was moved once through only one coil. The higher linear velocity means a better scrubbing action on the fin surfaces and a more effective heat transfer action.

AIR FLOW

The air flow path is designed to be more conducive to improved heat transfer because of the superimposed relation of the two coils. Inter-surface tube temperatures from the warmer to cooler tubes (as the refrigerant gas condensing action is being performed) are not transmitted because a normal heat transfer path of migration to the cooler edge is customary. The low temperature cooling air first flows past the lower cooler coil where it is heated; the increased volume flow (higher cubic feet) then flows across the upper coil at a somewhat higher linear velocity. This invention results in improved counter flow heat transfer without inter-tube surface temperature migration, combined with an air heat rise expansion plenum area (within the unit itself) to eliminate air flow pressure hold-back (due to air heating and expanding inter-fin such as on multi-row depth coils).

NOISE EMISSION

In the FIG. 4 arrangement, the fan 44 and compressor 48 are located upstream with respect to heat exchange coil 16b. This coil therefore acts as a barrier or absorber with respect to sounds emitted by the fan and compressor. This is an advantageous feature in residential air conditioners where houses may be rather close together.

REFRIGERANT FLOW VELOCITY

As the refrigerant flows through the condenser tubes some of the refrigerant condenses before it reaches the outlet of the condenser. The condensed refrigerant occupies less tube cross-section than the gaseous refrigerant so that the effective passage cross-section for refrigerant gas flow increases from inlet end of the condenser to the outlet end. The increased refrigerant gas flow flow passage area causes a reduction in the linear flow rate of the gas near the outlet end of the condenser. A low gas flow rate is undesirable because it means a lesser resultant refrigerant flow tube loading, whereas the refrigerant thermal coefficient (f.sub.2 --B.t.u./Hr/sq.ft./.degree.F) is reduced.

FIG. 10 illustrates a refrigerant flow passage arrangement which can be used to maintain a satisfactorily high refrigerant flow velocity along the length of the condenser from the inlet end to the outlet end. As shown in FIG. 10, the gaseous refrigerant enters through header 42 and flows through six relatively large diameter tubes 18b to a second header 44a which connects with a subjacent header 44b. All of the refrigerant then flows through two smaller refrigerant tubes 18a to another header 42a. Condensation occuring along the lengths of the tubes 18b tends to reduce the refrigerant velocity toward the downstream ends of these tubes, but the smaller diameters of tubes 18a and/or the lesser numbers of tubes 18a tends to restore the velocity to a satisfactory level. In a similar manner the diameters of the next tubes 18a can be reduced to obtain a satisfactory flow velocity in the lower tubes.

Comparing FIGS. 4 and 10, the FIG. 10 assembly comprising header 42, tubes 18b and header 44 forms the upper coil 16b in FIG. 4. The FIG. 10 assembly comprising the remaining headers and lower tubes 18a forms the lower coil 16a in FIG. 4.

SQUARE SHAPE

It will be seen from FIG. 5 that when the tubes 18a are bent into the rectangular shape the arcuate corner portions of the tubes cause the fins to be spaced relatively far apart at the outer edges of the fins and relatively close together at the inner edges of the fins. The closeness of the fin inner edges somewhat impedes air flow through the fin spaces and thereby makes the corner portions of the heat exchanger less efficient than the flat side portions. It is desirable to minimize arcuateness in the assembly, and accordingly it is preferred to use a square shape as shown in FIG. 5 in preference to a round circular shape. If desired the fins can be removed from the corner areas shown in FIG. 8. In that event it would be necessary to provide corner baffle sheets 60 to preclude undesired air flow around the fins. Such baffle sheets would of course extend the full length of each coil.

SINGLE COIL CONSTRUCTION(FIG. 9)

FIG. 4 shows two connected separate coils one above the other. However, it is believed possible to employ one single coil extending the entire height of the package. FIG. 9 fragmentarily shows a single height coil having suitable brackets 50b connected to selected heat exchange tubes, as by the tube-expansion procedure previously outlined. Each bracket projects inwardly below the venturi panel 34a. In this instance the venturi panel is provided with a downturned peripheral flange 35b fitting into a notch in each bracket 50a. In this manner it is believed possible to incorporate the venturi panel midway between the top and bottom panels 30 and 32(FIG. 4) while still using only one annular coil (instead of two coils as shown in FIG. 4).

The FIG. 9 arrangement may suffer somewhat in that the venturi panel does not bisect the coil so that air exhausted from fan 44 can more easily recycle as shown by arrow 62. Such recycling is not desirable in that the recycle air is heated air that does not have quite as satisfactory a heat transfer characteristic as fresh air coming in through the blower portions of the coil.

ACCESS TO COMPRESSOR

In the FIG. 4 arrangement access to the compressor may be had by unthreading the various nuts 58 and lifting off the assembly comprising panel 32, cone 46 and the fan. In the event it is desired to remove the compressor it may be necessary to first remove panel 34.

Preferably the compressor 48 outlet is connected to upper coil 16b by a tube of sufficient length to dissassembly of the coil without breakage of the fluid connection. Also, advantageously manual disconnect valves can be provided in the fluid connections to facilitate compressor replacement and system recharging.

The annular nature of coils 16a and 16b tends to prevent easy connection of the compressor with its supply voltage and refrigerant lines. However the dished character of panel 30 enables electrical wiring and fluid lines to be run into the interior space circumscribed by the coil, i.e., through the sidewall of the dish or surrounding land area. Thus, the arrangement is believed practical and adapted to fairly easy repair procedures when necessary.

A principal feature of the invention is the coil-fan relation wherein the fan has draw-through action with respect to one section of the coil and blow-through action with respect to another section of the coil. This arrangement is believed to promote high linear air velocities and improved heat transfer operation on the air side.

A cooperating feature of the invention is the annular character of the coil or coils which provides a large coil face area in a small volume package. The desirable result is achieved with a minimum quantity of non-useful "dead" casing wall area, since the only casing components are the three panels 30, 32 and 34. These panels may be formed, at least partly, using a common die, which makes for some manufacturing economy. Suitable materials such as steel, aluminum, or plastic may be used.

Claims

I claim:

1. A refrigerant condenser comprising fluid connected condenser coil sections wherein each coil section is an upstanding coil of generally annular configuration in plan outline with tubes extending there around and arranged one above another and said coil sections are stacked one above the other to provide a stacked coil assembly, means at each end of the stacked coil assembly to block the flow air through the ends of the assembly and a fan located in the space circumscribed by the coils with its axis of rotation generally extending in the direction of the axis of the stacked coil assembly and the blades of the fan located between the ends of the stacked coil assembly for drawing air into the circumscribed space through that portion of the coil assembly which extends from one end thereof to the fan blades and for blowing air from said circumscribed space through that portion of the coil assembly which extends from its other end to the fan blades.

2. The combination of claim 1 which includes a venturi panel between coil sections and has said fan blades located in the venturi opening.

3. The combination of claim 1 wherein the coil sections comprise connected refrigerant passages of which some are sized larger than others to at least partially compensate for different gas volumes handled by the respective passages.

4. The combination of claim 3 wherein larger sized refrigerant passages are elevated above smaller sized passages to promote drainage of condensed refrigerant through the coil sections.

5. A refrigerant condenser comprising coil means of generally annular configuration in plan outline with tubes extending there around and arranged one above another, means at each end of the coil means for blocking the flow of air through the ends thereof, and a fan located in the space circumscribed by the coil means with its axis of rotation generally extending in the direction of the axis of the coil means and the blades of the fan located between the ends of the coil means for drawing air into the circumscribed space through that portion of the coil means which extends from one end thereof to the fan blades and for blowing air from said circumscribed space through that portion of the coil means which extends from its other end to the fan blades.

6. The combination of claim 5 which includes a venturi panel between opposite ends of the coil means and has said fan blades located in the venturi opening.

7. The combination of claim 6 wherein the coil means comprises connected refrigerant passages of which some are sized larger than others to at least partially compensate for different gas volumes handled by the respective passages.

8. The combination of claim 5 including a refrigerant compressor in said circumscribed space between one end of the coil means and the fan blades.

9. The combination of claim 5 wherein the coil means has a generally square planar outline.