Patent Application
20160334117
The present invention relates to an induction supply air terminal device where primary air flow is used to induce a secondary air flow with increased air induction ratio.
An induction supply air terminal device essentially comprises of a primary supply air chamber, mixing chamber and at least one heat exchanger. From the primary supply air chamber the primary air is supplied out via one or several nozzles into a mixing chamber. The secondary air is conducted into the mixing chamber through a heat exchanger, where this secondary air can be heated or cooled. The primary supply air induces secondary air and they both mix in the mixing chamber. This mixed air is then conducted into the air-conditioned room space.
The present invention provides such an induction supply air terminal device, wherein the air induction ratio between the primary air and the secondary air is increased without compromising on equipment capacity, or resulting in enhanced energy costs, or outside (primary air flow) requirements.
Room space air handling solutions often comprise supply of air via a cooling or heating or chilled beam. In such a chilled beam, the supply air is supplied to the room, while a certain room air volume is sucked in through induction effect into a mixing chamber through a heating or cooling coil and is thereby heated or cooled therein, and then mixed with the supply air and circulated back into the room.
Chilled beams are components of air treatment systems used for cooling, heating, or ventilation purposes. Cooling beams or heating beams or chilled beams as they are generally referred to, provide several advantages for spaces of designated volumes in that the cooling or heating capacity can be satisfied by different modes such as supply of cold or hot water piped to the chilled beam rather than by requiring air handling units to handle the entire cooling or heating load.
Chilled beams can be either passive or active, depending on the nature of the convection process that is adopted. Passive chilled beams adopt a natural convection process where the air treatment device is provided in a box that is recessed or hung from a ceiling. In active chilled beams, ventilation air is introduced into the pressurized chamber, also referred to as plenum or supply air chamber, and then through small air nozzles in order to enhance the natural convection of air.
An important consideration in any chilled beam system is that the moisture content of the room air must necessarily be below dew point conditions. This is important to avoid the condensation in the chilled beam or water pipes surfaces. Dew point conditions are typically determined based on the coldest temperature on the surface of the chilled beam. Internal latent load is removed through ventilation only if the primary air is sufficiently dry and also present in high volume. Traditional dehumidification technology required a stipulated minimum required ventilation rate in order to keep the moisture level of indoor air at a desired level since moisture removal was limited in these technologies. Improvements in dehumidification technologies in air handling units have meant that greater dehumidification of air is possible, thereby lowering the minimum required ventilation rate even further or as may be mandated by code or design.
An active chilled beam's cooling capacity is based on the amount of room air (secondary air) circulating through the heat exchanger. This secondary air volume is dependent on the induction ratio of nozzle and the primary air volume. Now when primary air volume can be reduced, the induction ratio has to improve in order to keep the secondary air volume and thus the cooling capacity the same.
The following table exemplifies some of the challenges/issues in increasing air induction ratios:
To have the highest possible induction with lowest possible primary air flow rate is beneficial in terms of HVAC-system energy use. The induction ratio should be the highest possible with the lowest possible primary air flow and shortest possible induction length.
In current products, induction ratio is controlled by changing the nozzle size. Smaller nozzles have respectively higher induction ratios due to higher perimeter length compared to same total area of nozzles with bigger diameter. When nozzle becomes bigger, the air jet diameter in discharge slot becomes bigger and therefore the minimum distance between nozzles also increases. This limits the number of nozzles per linear length of beam. Respectively, with small nozzle the maximum primary air volume is limited based on the chamber pressure. Another concept to increase induction ratio is to shape the nozzle such that with same face area the perimeter length of nozzle is longer. This can be achieved by shaping the nozzle as flower instead of a circle. Third method is to have a venturi in the mixing chamber.
As can be seen, several methods have been proposed in the art to enhance or increase air induction ratios. Some of the solutions include modifying the nozzles or holes intended for pass-through of supply air.
These solutions provided for in the art, include variations in the designs of the nozzles or holes through which the primary air passes, exits and where the air flow after these holes makes the condition for the re-circulating room air to reach a mixing zone where both air flows are brought together prior to flow out into the room. The flow out from the pressure chamber is controlled by a number of holes or nozzles which are configured to different forms.
This type of device typically has several nozzles to induce the secondary air flow. These nozzles can be either holes, slots, punched collars, conical shaped???), or any other shape. In case of multiple nozzles, they may be arranged in such a manner that they form one or several elongate row. Smaller nozzles have higher induction ratio, but also smaller primary air flow rate at any given static chamber pressure. The size of the nozzle is selected in order to supply the required primary air flow at a given primary air chamber pressure.
An induction supply air terminal device is used with various primary air flow rates, therefore the same device may comprise of bigger and/or smaller nozzles or nozzles with adjustable face area for setting the desired supply air flow. Common for the solutions is the ratio between the primary and secondary air quantities is controlled so that the desired primary air flow and cooling/heating capacity is met. Examples of known solutions are described in WO 98/09115, where the induction supply air terminal device includes a primary air chamber where several nozzles or discharge opening exists.
EP 1 188992 A2 with characterized discharge holes (nozzles here) comprises of two groups (7, 8) that are laterally directed in different directions. These consist of two elongated slots (13, 16) equidistantly placed and having adjustable area for setting the desired supply air-flow.
Likewise, WO 2011/040853 A1 with characterized discharge holes of different sizes are comprised in different groups. At any given point of time each group can have only one active discharge hole, wherein these active discharge hole in each group are of similar characteristic and equidistantly placed from the active hole in the adjoining group. It is used to regulate the primary air-flow rate.
WO 96/28697 and EP 0 813 672 B1 describes a nozzle with scallop-shaped outlet edge. This has an effect on reducing noise output from the nozzle and improves mixing of primary and secondary air flow thereby increasing the rate at which the primary air flow can induce the secondary air flow. In this example the preferred nozzle shape has a perimeter to cross-sectional area ratio that is equal to or greater than 1.3 times the perimeter to cross-sectional area ratio for a circle of the same area.
While smaller nozzles have bigger induction ratio, the smaller face area means that they are not able to supply as much primary air as bigger nozzles and therefore also the amount of induced secondary air flow is smaller. Reducing the distance between the nozzles (d) to a value smaller than the diameter of the air jet (h), results in reduced induction length (l) and thereby reduced secondary air flow.
Another method to induce a higher level of secondary air flow is to use a venturi inside a mixing chamber. The venturi increases the secondary air flow when its neck size is equal to that of the diameter of the of the air jet. It is also seen that when the air jet central line velocity is higher, the effect of the venturi is better. Therefore, with the small air flow rate, the optimum location of the venturi is closer to the nozzle than that with the higher air flow rate. Based on varying needs, this induction supply air terminal device can be used with different air flow rates and therefore with adjustable venturi location.
As an example EP 0 813 672 B1 describes an induction supply air terminal device with a mixing chamber comprising of a fixed venturi having generally a circular cross-section of varying diameter along its length.
Optimal venturi location and diameter is dependent on the primary air volume and nozzle size. Different combinations give different jet sizes in the venturi neck. If the neck diameter is too small or too big compared to the jet diameter or is located in the non-optimum distance from the nozzle, as it may be a case with fixed venturi, it is not effectively increasing induction or may even reduce it.
The present invention firstly increases the induction near the nozzle due to having many smaller nozzles (cluster) with higher perimeter area compared to face area supplying the air from the pressurized plenum to a mixing chamber. Secondly, the adjustable venturi allows to locate the venture neck optimally and therefore further increase the induction near the discharge opening. This combination gives the highest induction ratio and therefore allows the design of an active chilled beam, where lower primary air volume gives the required cooling capacity per linear meter.
The state-of-art operation of device and innovation is described in the enclosed drawings, wherein
The present invention relates to an induction supply air terminal device where primary air flow is used to induce a secondary air flow wherein the nozzles are provided in the form of a cluster arrangement, comprising one or more clusters of three or more nozzles each. The clusters can be arranged according to predetermined patterns depending on the pattern of air induction that is desired.
The present invention also provides an induction supply air terminal device equipped with an adjustable venturi, where both the distance and the neck size can be adjusted based on the primary air volume and the nozzle surface area.
In another embodiment, the present invention also provides an induction air terminal supply device where the primary airflow is used to induce a secondary air flow wherein the nozzles are provided in the form of a cluster arrangement comprising one or more clusters of three or more nozzles each, and therein a venture device is provided to enhance the flow of secondary air. The venturi can be either a fixed venturi or an adjustable venturi.
In the present invention, the nozzle arrangement comprises a cluster of small nozzles instead of being placed equidistant in an elongate row. The clusters can be formed of different patterns as is depicted in
The resultant induction ratio of an air jet created by an array of multiple nozzles in a cluster is bigger compared to the induction ratio of an air jet of single nozzle with the same face area as of the clustered nozzles together.
A cluster can have an array of nozzles starting from 3 in number to more, based on the required surface area to be catered to.
The secondary air flow induced by primary air flow from a single nozzle of surface area equivalent to that of an array of multiple nozzles in a cluster is smaller than the secondary air flow induced by the same amount of primary air flow from a cluster of multiple nozzles.
Accordingly, the present invention provides an induction supply air terminal device that comprises of primary supply air chamber (1), at least one mixing chamber (2) which opens into the air-conditioned room space, at least one or no heat exchanger (3) The device is provided with an array of multiple nozzles in a cluster (5) that supplies primary air flow (4) into at least one mixing chamber (2) to induce a secondary air flow (6) heated or cooled as it flows through a heat exchanger (3) and conducted into the mixing chamber (2), wherein both this primary supply air (4) and secondary air (6) mix, whereby this mixed air (7) is then conducted into the air-conditioned room space (8) with an increased induction ratio.
In one embodiment, the array of multiple nozzles in a cluster can have three or more number of nozzles.
In another embodiment, the nozzles in a cluster can be circular, rectangular, elliptical or scalloped in shape.
In yet another embodiment of the invention, the nozzles in a cluster can be holes or punched collars in a sheet metal plate or conical nozzle that is fixed over the opening in the sheet metal.
In another embodiment of the invention, the nozzles in a cluster can be either made of metal (steel or aluminium), plastic or rubber.
In a preferred mode of the invention, the air jets from a cluster of multiple nozzles create multiple air jet zone of length (l1) that converge into a single air jet at a distance forming into a single air jet zone of length (l2).
In a further embodiment, the distance (d1) between an array of nozzles in a cluster is smaller than the distance (d2) between any two clusters of nozzles.
In the embodiment where air induction ratio is enhanced by use of an adjustable venturi, whether used in combination with a single nozzle or multiple nozzles in clusters or otherwise, the resultant induction ratio of an air jet created by a nozzle or an array of multiple nozzles in a cluster in combination with a venturi is larger than when compared to the induction ratio of an air jet resulting from nozzles alone.
Turning now to
Referring now to
In the embodiment comprising use of a venturi device whether in combination with a solo nozzle or nozzle clusters, the induction supply air terminal device that comprises of primary supply air chamber (1), at least one mixing chamber (2) which opens into the air-conditioned room space, at least one or no heat exchanger (3), single or an array of multiple nozzles in a cluster (5) that supplies primary air flow (4) into at least one mixing chamber (2) to induce a secondary air flow (6) heated or cooled as it flows through a heat exchanger (3) and conducted into the mixing chamber (2), wherein both this primary supply air (4) and secondary air (6) mix, whereby this mixed air (7) is then conducted into the air-conditioned room space (8), wherein an adjustable venturi (9) is provided to increase the secondary air flow rate (6).
In one embodiment, the location (x) of the venturi (9) is based on the optimum central line velocity (v) in the venturi neck, which depends on the primary air flow rate (4), the face area of the nozzle(s) and the secondary air flow (6).
In another embodiment, the neck diameter (y) of venturi is set equal to the diameter (h) of the air jet at the same location (x).
In another embodiment, the location (x) of the venturi (9) and/or the neck diameter (y) of the venturi (9) is adjusted manually or automatically using an actuator. In another embodiment, the venturi (9) shape and type can vary—solid, inflatable or bent metal/plastic sheet fixed at one end and with an adjustable another end.
It is observed through experiments carried out that there is a definite enhancement in the air induction ratios using the various arrangements embodied in the invention, viz.
(a) a cluster nozzle arrangement with a fixed venture;
(b) an adjustable venture with a single nozzle
(c) an adjustable venture with a cluster of nozzles
(d) chilled beams provided with each of the above combinations.
This data is summarised in the Table below:
| Number | Date | Country | Kind |
|---|---|---|---|
| 125/DEL/2014 | Jan 2014 | IN | national |
| 126/DEL/2014 | Jan 2014 | IN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IN2015/000021 | 1/15/2015 | WO | 00 |
