WO2020187829A1

WO2020187829A1 - Fan coil air conditioning system

Info

Publication number: WO2020187829A1
Application number: PCT/EP2020/057081
Authority: WO
Inventors: Paul Freeman; Geoff LOCKWOOD
Original assignee: Basic Holdings; Ability Projects Limited; Ebm-Papst Uk Limited
Priority date: 2019-03-15
Filing date: 2020-03-16
Publication date: 2020-09-24
Also published as: GB2582546A; GB2582546B; GB201903577D0

Abstract

A fan coil that includes a backward curved centrifugal fan is described.

Description

Title

Fan Coil Air Conditioning System

Field

The present application relates to fan coil air conditioning systems and in particular to a fan coil system comprising centrifugal fans with backward-curved blades.

Background

Fan coil systems are generally known. An example is described in GB 2433586 which describes such systems typically comprise a chamber comprising a coil through which temperature-controlled fluid flows. Air is drawn into the chamber and over the coil using a fan. The temperature and or volume of the air is thus controlled by the temperature of the fluid flowing through the coil. The air is then pumped from the chamber to the appropriate part of a building through air delivery ducts connected to the chamber.

These known fan coil systems conventionally use centrifugal fans. The name, centrifugal fan is derived from the direction of flow and how the air enters the impeller in an axial direction and is then propelled outwards from the outer circumference of the fan. There are different types of centrifugal fans including those with forward curved and backward curved blades. With a forward curved blade fan, the blades of the impeller are angled in a direction such that they curve towards the direction of rotation. In contrast, with a backward curved fan, the blades curve away from the direction of rotation. As a result of this difference in orientation there is a subsequent difference in flow direction between a forward and backward curved centrifugal fan. With a backward curved impeller, the air exits in a radial direction whereas with a forward curved the air exits tangentially from the circumference of the fan.

Forward curved fans are especially sensitive to particulates and commonly are only specified for clean-air applications such as air conditioning where their low noise characteristics are appreciated. They are particularly suited for use in fan coil systems where air is drawn through the chamber within which the fan is located and out through a ducting arrangement. The ductwork that is used in the fan coil systems is typically standardised in size and the dimensions of the forward curved fans are particularly suited to this standardised dimension.

Figure 1 shows in schematic form, an example of a known fan coil system 100. A forward curved fans 110 is provided within a conduit 120 having at a first end 131 a coil 130 through which temperature-controlled fluid flows. Air 135 is drawn over the coil and enters an inlet 125 of the fan. Per standard operation of a forward curved fan, the air enters via the inlet 125 which is provided on a side wall of the fan unit. The air is redirected through about 90 degrees and exits through an exit 126 which is substantially perpendicular to the inlet. The air then exits the conduit 120 through an exit port 132 provided in a second end 133 of the conduit- the second end being opposite the first end 131. It will be understood that the conduit 120 has a primary longitudinal axis extending between the first 131 and the second 133 ends of the conduit, the air following a path that is substantially parallel to this axis.

Figure 2 shows in schematic form an example of such a forward curved fan 200 which comprises a plurality of forward curved blades 210 arranged in a disc (not all blades are evident in this schematic). The disc or impeller rotates in this example in a clockwise direction. Each blade has a suction side 230 and a pressure side 220. The air exits the impeller radially in a tangential direction.

Despite the prevalence of these known fan coil systems there continues to be a need for improved fan coil systems.

Summary

These and other problems are provided in accordance with the present teaching by a fan coil system comprising a conduit having an entry port through which air is operably drawn into the conduit and an exit port through which the air operatively exits the conduit, the system further comprises a coil provided proximate the entry port and through which a temperature-controlled fluid operatively flows and a backward curved fan provided within the conduit and configured to assist movement of the air from the entry port to the exit port. In preferred configurations the performance of the system can be further enhanced by having the backward curved fan inclined relative to a longitudinal axis of the conduit.

The coil is typically orientated in a plane transverse to the longitudinal axis of the conduit and occludes the entry port of the conduit. In this way, air that is drawn into the entry port is passed across the coil and will be heated or cooled by passing proximate to the temperature- controlled fluid, depending on the relative temperature of the fluid to the air.

The conduit typically has a bottom surface, a top surface and side walls extending from the bottom surface to the top surface, the inclination is desirably a horizontal inclination relative to each of the top and bottom surfaces.

The inclination of the fan relative to the longitudinal axis of the conduit is desirably at an angle of between 10 and 30 degrees relative to the horizontal, desirably less than 15 degrees.

The fan is desirably orientated such that air passing from the conduit entry port enters upwardly into the fan and then passes out from the fan, the fan directing the air towards the conduit exit port.

The system may optionally comprise an angled deck plate provided within the conduit between the entry port and the exit port. The deck plate extends between the side walls of the conduit, the fan being mounted on, or to, the deck plate, the fan providing an air passage through the deck plate. The deck plate desirably also extends from the top surface to the bottom surface of the conduit. The deck plate comprises a mounting surface supporting the fan and may additional comprise a baffle surface, the baffle surface being angularly offset from the mounting surface. The baffle surface, where provided, extends upwardly from the bottom surface of the conduit. The baffle surface may, in certain configurations, be substantially perpendicular to the bottom surface of the conduit and operatively spaces the inlet of the fan away from the bottom surface of the conduit.

The system may further comprise a plenum chamber provided within the conduit and within which the fan is located, the plenum chamber having an outlet downstream of the fan through which air can exit the chamber.

Operatively air enter into the plenum chamber through the inlet of the fan and exits through an open face of the plenum chamber, the open face being provided proximate to the exit port of the conduit. The plenum chamber may define a closed volume defined between the fan and side walls of the plenum chamber. Operatively, air passes into and out of the closed volume through the fan.

Accordingly, there is provided a fan coil system as detailed in claim 1. Advantageous embodiments are provided in the dependent claims.

Brief Description Of The Drawings

The present application will now be described with reference to the accompanying drawings in which:

Figure 1 is a schematic side view showing a known fan coil system incorporating a forward curved fan

Figure 2 shows the principle of operation of a forward curved fan

Figure 3 shows the principle of operation of a backward curved fan.

Figure 4A is a schematic side view showing a fan coil system incorporating a backward curved fan in accordance with the present teaching. Figure 4B is a schematic plan view from above of the fan coil system of Figure 4A in accordance with the present teaching.

Figure 5 shows an open mounting arrangement for first and second fans in accordance with the present teaching.

Figure 6 shows a closed mounting arrangement for first and second fans in accordance with the present teaching where each fan is provided within a dedicated fan cassette.

Figure 7 is a schematic side view showing a fan coil system incorporating a backward curved fan in accordance with the present teaching.

Figure 8 is a schematic side view showing a fan coil system incorporating a backward curved fan in accordance with the present teaching.

Figure 9 is a schematic side view showing a fan coil system incorporating a backward curved fan in accordance with the present teaching.

Figure 10 shows a simulation result of air flow through a fan coil system in accordance with the present teaching.

Detailed Description Of The Drawings

In accordance with the present teaching a fan coil system incorporates a centrifugal fan that includes backward curved blades. Such fans per se are well known and are characterised by their cylindrical shape, several large curved blades and a conical inlet nozzle. Figure 3 shows in schematic form, similar to that shown in Figure 2, of an example of such a backward curved fan 300 which comprises a plurality of curved blades 310 arranged in a disc (not all blades are evident in this schematic). The disc or impeller rotates in this example in a clockwise direction. Each blade has a suction side 330 adjacent to the concave side of the blade and a pressure side 320 provide on the convex side of the blade. The air exits the impeller with radial centrifugal force. As the fan rotates a pressure difference is created on the impeller blades 310. On the leading, convex side 320, a positive pressure is created as the rotational motion of the impeller imparts a force in the air. The impeller blade pushes the air outwards, exiting in a radial direction. On the concave side 330, a negative pressure is created as the fan rotates, drawing air into the space between the blades. This air is then picked up by the following blade and forced outwards radially in a continuous process. The suction side 320 draws air from the centre of the fan which results in a directional change of the airflow between the inlet and the exhaust of 90 degrees.

Such a fan can be incorporated into a fan coil system 400 such as that detailed in Figures 4A and 4B. In this arrangement, and similarly to that described above with reference to known fan coil systems that include fans with forward curved blades, a fan coil system 400 in accordance with the present invention comprises a conduit 420 having an entry port 430 through which air is operably drawn into the conduit and an exit port 432 through which the air operatively exits the conduit.

The entry and exit ports are provided at first and second ends of the conduit respectively. Similarly to known arrangements, the system further comprises a coil 431 provided proximate the entry port 430 and through which a temperature-controlled fluid operatively flows. The coil is typically orientated in a plane transverse to the longitudinal axis of the conduit and occludes the entry port of the conduit. In this way, air that is drawn into the entry port is passed across the coil and will be heated or cooled by passing proximate to the temperature- controlled fluid, depending on the relative temperature of the fluid to the air.

In contrast to the known arrangements, in accordance with the present teaching a backward curved centrifugal fan 410 is provided within the conduit 420 and is configured to assist a movement of the air from the entry port 430 to the exit port 432. The present inventors have identified that the backward curved fan 410 is optimally orientated at an inclination within the conduit. By inclining the fan relative to the longitudinal axis A-A’ of the conduit, air that enters through an inlet 425 of the fan impeller maintains smooth and laminar characteristics that maximise the efficiency of the impeller blade allowing it to operate with reduced turbulence induced noise, keeping the power consumption at the duty point to a minimum and maximises efficiency of use of the fan. The inlet 425 of the fan is provided proximal to the inlet port 430 of the conduit.

In this way and as is seen from Figure 4A, the fan 410 is orientated such that air passing from the conduit entry port 430 enters downwardly into the fan through the fan inlet 425 and then passes out from the fan through a fan outlet 426, the fan directing the air towards the conduit exit port 432. In accordance with known operation of centrifugal backward curved fans, the air is deflected through 90 degrees between passing into and exiting from the fan.

The conduit has a bottom surface 450, a top surface 451 and side walls 452, 453 extending from the bottom surface to the top surface and separating the top from the bottom. As is evident from inspection of Figure 4A, the inclination is desirably a horizontal inclination relative to each of the top 451 and bottom 450 surfaces. Optimally the inclination is between 10 and 30 degrees, desirably less than 15 degrees. In other configurations, not shown, the inclination can be a vertical inclination relative to the side walls. In certain configurations the inclination is in two planes, vertical and horizontal relative to the side and top/bottom surfaces of the conduit respectively. Per the present teaching the fan is inclined in at least one plane within the conduit.

To achieve the inclined orientation of the fan within the conduit, the system optimally comprises comprises an angled deck plate 440 provided within the conduit between the entry port and the exit port. The deck plate extends between the side walls 452, 453 of the conduit, the fan 410 being mounted on, or to, the deck plate. As the deck plate extends across the conduit and desirably also extends from the top surface 451 to the bottom surface 450 of the conduit it serves to constrain the passage of air through the conduit. The deck plate is a solid structure with an aperture defined therein. The aperture is coincident with the location of the fan inlet 425 such that the fan provides an air passage through the deck plate. All air passing from the air inlet port 430 to the exit port 432 must therefore pass through the fan 425.

The deck plate 430 comprises an inclined mounting surface 441

supporting the fan and may additional comprise a baffle surface 442, the baffle surface being angularly offset from the mounting surface. The baffle surface, where provided, extends upwardly from the bottom surface 450 of the conduit. The baffle surface in this arrangement is provided at 90 degrees to the mounting surface, but may, in certain configurations such as those shown in Figures 7-8, be substantially perpendicular to the bottom surface 450 of the conduit. In all configurations it operatively spaces the inlet 425 of the fan away from the bottom surface 450 of the conduit.

Whilst a fan coil system in accordance with the present teaching may include one fan, as shown in the plan view of Figure 4B, two or more fans 410 may be provided. Each fan will have an inlet 425 such as that described above.

As shown in Figures 5 and 6, where two or more individual fans are provided, they may be provided in an open (Figure 5) or a closed (Figure 6) arrangement on the deck plate 430. In Figure 5 which shows an open mounting arrangement, the first and second fans 410 are visible on the top surface 500 of the deck plate 430. In contrast in Figure 6 which shows a closed mounting arrangement, each fan is provide within a dedicated fan cassette 610 such that the fans are not actually visible. Figure 7, 8 and 9 show variations to the arrangement of Figures 4 where the same reference numerals are used for similar parts. In the arrangement of Figure 7, an angled fan deck plate is configured to accommodate both open and closed cassettes- similar to each of the arrangement of Figures 5 and 6. In contrast, in Figure 8, a vertical infill panel is provided and this arrangement is better suited for a closed cassette. Figure 9 again uses an infill panel, but in this arrangement, the infill panel is angled so as to baffle at the outlet 426 of the fan the outwardly directed air.

Examples of relative performances of each of these fan configurations relative to a prior art arrangement per Figure 1 is exemplified below in Table 1.

It will be appreciated that the arrangement of Figure 4 provides good sound and power characteristics and it is believed that these are derived from the presence of the physical barrier between the inlet 425 and outlet port 432 which aids the transport of air by reducing internal turbulence.

The system on any one of the closed cassette configurations defines a a plenum chamber 460 provided within the cassette 610 within which the fan is located, the plenum chamber being closed on at least three sides. Operatively air enters into the plenum chamber 460 through the inlet of the fan and exits through an open face of the plenum chamber coincident with the exit 426 of the fan. In this way, the open face is provided proximate to the exit port 432 of the conduit. As shown in Figure 6, the plenum chamber defined within the cassette may define a closed volume defined between the fan and side walls of the plenum chamber. Operatively, air passes into and out of the closed volume through the fan.

By inclining the fan relative to the longitudinal axis of the conduit, the present inventors have realised that improved laminar flow through the conduit can be achieved with reduced noise level arising from less turbulence. Figure 10 is an example of simulation effects showing how the laminar flow through conduit 820 is achieved with an inclination of deck plate.

Using an arrangement per the present the teaching it is possible to fit a centrifugal fan with backward curved blades into a fan coil conduit. The efficiencies that are associated with physical larger centrifugal fans with backward curved blades are therefore achievable whilst at the same time the physical constraints that are associated with standardised conduit dimensions are met. The noise and power usage of fans in accordance with the present teaching as compared to a prior art arrangement are presented in Table 1 below and from this the improvements are evident, with less power usage and lower noise levels comparable air throughput is achieved.

Table 1

The words comprises/comprising when used in this specification are to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers , steps, components or groups thereof.

Claims

1. A fan coil system comprising a conduit having an entry port through which air is operably drawn into the conduit and an exit port through which the air operatively exits the conduit, the system further comprising:

a coil provided proximate the entry port and through which a

temperature-controlled fluid operatively flows;

a backward curved centrifugal fan provided within the conduit

downstream from the coil and inclined relative to a longitudinal axis of the conduit, the fan being configured to assist movement of the air from the entry port to the exit port; and

wherein the system comprises an angled deck plate provided within the conduit between the entry port and the exit port, the deck plate extending between side walls of the conduit, the fan being mounted on, or to, the deck plate, the fan providing an air passage through the deck plate.

2. The system of claim 1 wherein the conduit has a bottom surface, a top surface and side walls extending from the bottom surface to the top surface, the inclination being a horizontal inclination relative to each of the top and bottom surfaces.

3. The system of any preceding claim wherein the inclination is at an angle of between 10 and 30 degrees relative to the horizontal, desirably less than 15 degrees.

4. The system of any preceding claim wherein the fan is orientated such that air passing from the conduit entry port enters upwardly into the fan and then passes out from the fan, the fan directing the air towards the conduit exit port.

5. The system of any one of claims 1 to 3 wherein the fan is orientated such that air passing from the conduit entry port enters downwardly into the fan and then passes out from the fan, the fan directing the air towards the conduit exit port.

6. The system of any preceding claim wherein the deck plate also extends from the top surface to the bottom surface of the conduit.

7. The system of any preceding claim wherein the deck plate comprises a mounting surface supporting the fan and a baffle surface, the baffle surface being angularly offset from the mounting surface.

8. The system of claim 7 wherein the baffle surface extends upwardly from the bottom surface of the conduit.

9. The system of claim 7 or 8 wherein the baffle surface is substantially perpendicular to the bottom surface of the conduit and operatively spaces the inlet of the fan away from the bottom surface of the conduit.

10. The system of any preceding claim comprising a plenum chamber provided within the conduit and within which the fan is located, the plenum chamber being closed on at least three sides.

11. The system of claim 10 wherein air operatively enters into the plenum chamber through the inlet of the fan and exits through an open face of the plenum chamber, the open face being provided proximate to the exit port of the conduit.

12. The system of claim 10 or 11 wherein the plenum chamber defines a closed volume between the fan and side walls of the plenum chamber and wherein operatively, air passes into and out of the closed volume through the fan.

13. The system of any preceding claim comprising a plurality of backward curved centrifugal fans.

14. The system of any preceding claim wherein the deck plate defines an aperture coincident with the inlet of the backward curved centrifugal fan such that air can operatively pass through the aperture and into the fan.