GB2109107A

GB2109107A - Method of and apparatus of individually cooling a plurality of rooms

Info

Publication number: GB2109107A
Application number: GB08231428A
Authority: GB
Inventors: Eduard Blaha
Original assignee: Sulzer AG; Gebrueder Sulzer AG
Current assignee: Sulzer AG
Priority date: 1981-11-06
Filing date: 1982-11-03
Publication date: 1983-05-25
Also published as: FR2516212A1; CH653117A5; DE3144715A1; FR2516212B3

Abstract

In a room cooling system operating with a variable quantity of cooling air, the primary air is cooled to at least 10 DEG C below the room air temperature of the room (15) to be cooled. This cool primary air is mixed in an induction system (1) with secondary air drawn in from the room (15) before the mixed air is ejected as cooled air into the room (15). Mixing the primary air and the room air before discharge into the room (15) enables primary air temperatures to be lower; consequently, smaller volumes of primary air are required for a given removal of heat than previously, so that the air-conditioning plant can be smaller - i.e., the space taken up thereby and its capital cost and power consumption can be reduced. Also, drawing in room air in an induction system (1) ensures that the mixture ratio between primary air and secondary air remains substantially constant for the different quantities of primary air required to produce different amounts of cooling. <IMAGE>

Description

SPECIFICATION Method of and apparatus of individually cooling a plurality of rooms This invention relates to a method of individually cooling a plurality of rooms by means of a central ventilating system which supplies from an air-conditioning plant to the various rooms air needed for renewal and humidification in the form of cooling air at a constant temperature considerably below room temperature, the quantity of injected cool air in excess of the minimum requirement being controlled by means of a room thermostat to control cooling. The invention also relates to apparatus for such cooling.

The method outlined is known, for instance, from Swiss patent specification 555 519 wherein the cold input is adapted by rate of flow control of the prepared and cooled primary air delivered by the air-conditioning plant. The cool primary air is directly injected into the room, preferably near the ceiling, where it mixes - i.e., only after it has issued into the room - with the room air because of the induction effect of its flow.

Practical experience with these known methods and apparatus for cooling have shown that, to ensure the comfort of the room occupants, the constant temperature of the injected primary air must be not more than from 8 to 1 0,C below the room temperature of approximately 26 to 28"C, otherwise the quantity of primary air, more particularly on a low cooling load, becomes so small that it has little induction effect, fails to mix adequately with the room air, "drops" into the room and forms cold islands near the floor.

Consequently, relative large quantities of primary air must be available for maximum cooling performance, so that the air-conditioning plant producing the primary air is correspondingly very expensive and takes up considerable space.

It is an object of the invention so to modify the known cooling method on the basis of variable primary air quantities that captial costs and energy costs associated with maximum cooling output are reduced. Also, apparatus to carry out the modified method should comply with the additional requirement that the ratio of primary air to induced secondary or room air remains at least substantially constant over the whole range of primary air flows injected into the room.

According to one aspect, the present invention provides a method of individually cooling a plurality of rooms by means of a central ventilating system which supplies from an airconditioning plant to the several rooms air needed for renewal and humidification in the form of cooling air at a constant temperature below room temperature, the quantity of injected cool air being controlled by means of a room thermostat to control cooling, the cool primary air supplied to the room by the airconditioning means being cooled to at least 10"C below room temperature and, before issuing into the room as cooling air, being mixed with room air drawn in as secondary air.

Since, in the method according to the invention, the primary air can for a given primary air temperature - i.e., the same temperature of the air reaching the room - be cooled more than previously - advantageously to form 1 2 to 1 8 C below room temperature the quantities of primary air required can be reduced substantially; consequently, all parts of the air-conditioning apparatus can be smaller and more compact and the power consumption needed for primary air conveyance can be reduced considerably. Advantageously - but not necessarily - the room air mixed with the cool primary air is taken from the room it is required to cool.

To maintain comfortable conditions in the region where the room occupants are, it has been found advantageous if the cool primary air and the room air are mixed together in a proportion of from 4:1 to 1:1; the optimum mixing proportion economically can be more particularly 3:2.

According to a second aspect of the present invention, apparatus for the individual cooling of a plurality of rooms comprises an air conditioning plant and a central ventilating system for supplying to the several rooms air needed for renewal and humidification in the form of cooling air at a constant temperature below room temperature, a cool air feed line leading to an air induction means for each room, and a room thermostat in each room connected to control the rate of flow of cooling air to the respective room, each air induction means including a pressure chamber from which discharge nozzles lead into an outlet chamber which is surrounded by a secondary air induction chamber having at least one inlet opening for room air.

Of course, apparatus constructed according to the invention must, just like the conventional apparatus, satisfy general requirements for silent operation and for the virtual absence of condensation on the cold parts of the apparatus. In this connection, very compact arrangements can be provided if the pressure chamber comprises a sound damper formed by sound-damping tubes of different diameters which telescope one within another and if at least part of the walls of the air induction means are sound-absorbing and/or heat-insulating.

As previously stated, one of the objects of the invention is to ensure that the proportions of primary air and induced secondary or room air remain at least substantially constant over the whole range of primary air flow rates. This is achieved because, while the room air is being mixed inside the induction system, the resistance to the induction of room air remains at all primary air rates of flow substantially in a fixed relationship to the exit speed of the primary air from the nozzle-like discharge orifices.Consequently, if the shaping of the discharge nozzles and/or the devising of the resistance for the flow of induced room or secondary air is given consideration in the design of the induction system, virtually a predetermined relationship between primary air and secondary air in the flow of air entering the room can be achieved; more particularly, the relationship can be such that the proportion of primary air is 60% and the proportion of secondary air is 40%.

Another considerable advantage of the invention is that it is possible to obtain a relatively low pressure loss in the induction system.

The invention may be carried into practice in various ways but one form of air-conditioning apparatus embodying the invention and its method of operation will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a view in plan, on the line I-I of Fig. 2, of an induction system forming part of the apparatus; Figure 2 is a section on the line ll-ll of Fig.

1; and Figure 3 is a section on the line Ill-Ill of Fig. 2.

Referring to Fig. 1, and induction system 1 is supplied through a line 2 with primary air prepared and cooled in an air-conditioning plant (not shown). The primary air line 2 extends into a casing 3 of the system 1 and terminates in a pressure chamber 4, the free end of the line 2 extending into the chamber 4 and comprising. a discharge controller 5 of known construction. The discharge controller is used in known manner to control the flow of primary air in dependence upon room temperature as detected by a room thermostat 6.

Disposed in the chamber 4 for sound damping are two telescopically engaging sounddamping tubes 7, 8 of different diameter from one another; the primary air in passing through the chamber 4 is compelled to zigzag through the tubes, so that satisfactory sound damping is provided despite the relative shortness of the tubes 7, 8.

Perpendicularly to the primary air inflow direction, the chamber 4 is bounded by a partition 9 formed with nozzle-like discharge orifices 10 so disposed that the streams Of primary air discharging from them are directed towards an outlet chamber 11 formed by a hollow parallelpiped-shaped member 1 2.

The chamber 11 terminates in an outlet orifice 14 which has a grid or lattice and through which the primary air is ejected into the room 15.

Extending around the member 1 2 is an induction chamber 1 6 which is bounded by the casing 3 and through which flows room air drawn in as secondary air by the "streams" of primary air, the room air being drawn along by these "streams" by way of a venturi-like annular gap 1 7 between the wall of member 1 2 and the partition 9. Room air enters the chamber 1 6 from the room 1 5 through a griddled intake opening 1 3 in the casing 3.

Advantageously, the induction system 1 is so arranged in the ceiling zone of the room 1 5 to be cooled that, as indicated in Fig. 2, the inflowing mixed air issuing from the opening 1 4 issues into the room 1 5 substantially horizontally and parallel to the ceiling, the intake opening 1 3 being in the bottom wall of the casing 3 - i.e., the room air being taken in upwardly.

To obviate the formation of condensation and to provide sound damping in addition to that provided by the sound damper 7, 8, the casing 3 and the member 1 2 are made of a material, such as glass wool or mineral wool, which is a sound and heat insulant. It may, however, be possible for only part of these components to be made of such a material.

In conclusion, an example will be given to show the effectiveness of the apparatus and its method of operation.

It will be assumed that the maximum quan tity of heat to be removed to maintain a constant temperature of 26"C in the room to be cooled is 700 W. To remove this amount of heat a primary air flow of 160 m3/h at a temperature of approximately 12.5"C enters the induction system 1. 110 m3/h of room air, as secondary air, is induced into the primary air flow in the system 1 by means of the primary air flow discharging from the chamber 4 through nozzles 10 at a speed of 11 m/sec.Consequently, the air issuing into the room through the grid 14 in maximum conditions of operations is 270 m3/h and is at a temperature of approximately 1 8 C. For minimum cooling the quantity of primary air at constant temperatures is 80 m3/h; this reduced primary air flow drawing in 55 m3/h of room air as secondary air, so that the inflow of air is 135 m3/h.

The component of primary air in the mixed pr inflow air is therefore constant at around just about 60%, as compared with a little over 40% for the room air.

CLAY MY 1. A method of individually cooling a plureality of rooms by means of a central ventilating system which supplies from an air-conditioning plant to the several rooms air needed for renewal and humidification in the form of :cooling air at a constant temperature below room temperature, the quantity of injected cool air being controlled by means of a room thermostat to control cooling, the cool primary

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. being mixed inside the induction system, the resistance to the induction of room air remains at all primary air rates of flow substantially in a fixed relationship to the exit speed of the primary air from the nozzle-like discharge orifices. Consequently, if the shaping of the discharge nozzles and/or the devising of the resistance for the flow of induced room or secondary air is given consideration in the design of the induction system, virtually a predetermined relationship between primary air and secondary air in the flow of air entering the room can be achieved; more particularly, the relationship can be such that the proportion of primary air is 60% and the proportion of secondary air is 40%. Another considerable advantage of the invention is that it is possible to obtain a relatively low pressure loss in the induction system. The invention may be carried into practice in various ways but one form of air-conditioning apparatus embodying the invention and its method of operation will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a view in plan, on the line I-I of Fig. 2, of an induction system forming part of the apparatus; Figure 2 is a section on the line ll-ll of Fig. 1; and Figure 3 is a section on the line Ill-Ill of Fig. 2. Referring to Fig. 1, and induction system 1 is supplied through a line 2 with primary air prepared and cooled in an air-conditioning plant (not shown). The primary air line 2 extends into a casing 3 of the system 1 and terminates in a pressure chamber 4, the free end of the line 2 extending into the chamber 4 and comprising. a discharge controller 5 of known construction. The discharge controller is used in known manner to control the flow of primary air in dependence upon room temperature as detected by a room thermostat 6. Disposed in the chamber 4 for sound damping are two telescopically engaging sounddamping tubes 7, 8 of different diameter from one another; the primary air in passing through the chamber 4 is compelled to zigzag through the tubes, so that satisfactory sound damping is provided despite the relative shortness of the tubes 7, 8. Perpendicularly to the primary air inflow direction, the chamber 4 is bounded by a partition 9 formed with nozzle-like discharge orifices 10 so disposed that the streams Of primary air discharging from them are directed towards an outlet chamber 11 formed by a hollow parallelpiped-shaped member 1 2. The chamber 11 terminates in an outlet orifice 14 which has a grid or lattice and through which the primary air is ejected into the room 15. Extending around the member 1 2 is an induction chamber 1 6 which is bounded by the casing 3 and through which flows room air drawn in as secondary air by the "streams" of primary air, the room air being drawn along by these "streams" by way of a venturi-like annular gap 1 7 between the wall of member 1 2 and the partition 9. Room air enters the chamber 1 6 from the room 1 5 through a griddled intake opening 1 3 in the casing 3. Advantageously, the induction system 1 is so arranged in the ceiling zone of the room 1 5 to be cooled that, as indicated in Fig. 2, the inflowing mixed air issuing from the opening 1 4 issues into the room 1 5 substantially horizontally and parallel to the ceiling, the intake opening 1 3 being in the bottom wall of the casing 3 - i.e., the room air being taken in upwardly. To obviate the formation of condensation and to provide sound damping in addition to that provided by the sound damper 7, 8, the casing 3 and the member 1 2 are made of a material, such as glass wool or mineral wool, which is a sound and heat insulant. It may, however, be possible for only part of these components to be made of such a material. In conclusion, an example will be given to show the effectiveness of the apparatus and its method of operation. It will be assumed that the maximum quan tity of heat to be removed to maintain a constant temperature of 26"C in the room to be cooled is 700 W. To remove this amount of heat a primary air flow of 160 m3/h at a temperature of approximately 12.5"C enters the induction system 1. 110 m3/h of room air, as secondary air, is induced into the primary air flow in the system 1 by means of the primary air flow discharging from the chamber 4 through nozzles 10 at a speed of 11 m/sec.Consequently, the air issuing into the room through the grid 14 in maximum conditions of operations is 270 m3/h and is at a temperature of approximately 1 8 C. For minimum cooling the quantity of primary air at constant temperatures is 80 m3/h; this reduced primary air flow drawing in 55 m3/h of room air as secondary air, so that the inflow of air is 135 m3/h. The component of primary air in the mixed pr inflow air is therefore constant at around just about 60%, as compared with a little over 40% for the room air. CLAY MY

1. A method of individually cooling a plureality of rooms by means of a central ventilating system which supplies from an air-conditioning plant to the several rooms air needed for renewal and humidification in the form of :cooling air at a constant temperature below room temperature, the quantity of injected cool air being controlled by means of a room thermostat to control cooling, the cool primary

air supplied to the room by the air-condition ing means being cooled to at least 1 0 C below room temperature and, before issuing into the room as cooling air, being mixed with room air drawn in as secondary air.

2. A method as claimed in Claim 1 in which the cool primary air is cooled to form 1 2 to 1 8 C below room temperature.

3. A method as claimed in Claim 1 or Claim 2 in which the cool primary air and the room air are mixed together in a proportion of from 4:1 to 1:1.

4. A method as claimed in Claim 1 or Claim 2 in which the cool primary air and the room air are mixed together in a proportion of 3:2.

5. A method as claimed in any of the preceding claims in which the room air is drawn in directly from the room to which it is delivered after mixing with cool air.

6. Apparatus for the individual cooling of a plurality of rooms comprising an air condi tioning plant and a central ventilating system for supplying to the several rooms air needed for renewal and humidification in the form of cooling air at a constant temperature below room temperature, a cool air feed line leading to an air induction means for each room, and a room thermostat in each room connected to control the rate of flow of cooling air the respective room, each air inductive means including a pressure chamber from which dis charge nozzles lead into an outlet chamber which is surrounded by a secondary air induc tion chamber having at least one inlet opening for room air.

7. Apparatus as claimed in Claim 6 in which the pressure chamber comprises a sound damper formed by sound-damping tubes of different diameters which telescope one within another.

8. Apparatus as claimed in Claim 6 or Claim 7 in which at least part of the walls of the air induction means are sound-absorbing and/or heat-insulating.

9. Apparatus as claimed in Claim 6 or Claim 7 or Claim 8 in which the shape and dimensions of the air passages into, through and out of the air induction means are such that in use of the mixed-air stream issuing from the outlet chamber contains substantially 60% cool primary air and 40% intaken secon dary air.

1 0. A method of individually cooling a plurality of rooms substantially as described herein with reference to the accompanying drawings.

11. Apparatus for the individual cooling of a plurality of rooms substantially as described herein with reference to the accompanying drawings.