Patent Application
20140231045
The invention relates to an induction displacement unit, and more particularly, to an induction displacement unit comprising an induction plenum communicating with a first discharge plenum and a second discharge plenum, the first discharge plenum in communication with a heating coil and the second discharge plenum in communication with a cooling coil.
Displacement ventilation systems are in wide spread use in the HVAC industry. One particular application for such systems is in educational buildings. Typically, a number of displacement air terminal devices will be located along a perimeter wall of a classroom space and are configured to deliver ventilation air to the space, see
Displacement ventilation (DV) is an air distribution system designed to simultaneously improve indoor air quality and reduce energy use. Cool, rather than cold supply air is provided directly to occupants through low mounted diffusers. Heat generated by the occupants and equipment in the space causes ventilation air to be naturally drawn up by convection which ensures fresh air is continually delivered to the breathing zone of the occupants. The warm air continues to rise and contaminants are carried away towards the ceiling exhaust, resulting in improved indoor air quality near the occupants. Schools, restaurants, theaters, atria, other open spaces with high ceilings, and spaces where air quality is a concern are excellent applications.
In addition to the displacement function, it is also known to configure displacement devices to have induction nozzles. By adding induction, room air from the space can be conditioned, filtered, and returned to the space in a mixture with the ventilation air. This type of unit is sometimes referred to as an induction-displacement unit. In this type of system, a coil is provided in the return air path of the induction-displacement unit to condition the return air, as necessary. In the cooling mode, the coil will reduce the return air temperature to a few degrees below the space temperature. In the heating mode, the coil may be set to raise the temperature of the return air such that the delivered air has a higher temperature than that of the air in the room.
In each mode a space temperature set point can be maintained, however, in heating mode, the induction-displacement unit can no longer function as a displacement terminal unit due to the fact that the delivered air starts rising as soon as it leaves the unit instead of pooling across the floor. To prevent placing an induction-displacement unit in the heating mode, a separate heating system can be provided in the space, such as fin-tube radiation or radiant panels. However, as the induction-displacement units are placed along at least one wall of the space, such heating systems cannot be placed in the same location. This is especially troublesome where the induction-displacement units are located along an exterior wall of the space because this is the location where heating is generally most needed. As such, improvements are desired for induction-displacement units that can simultaneously provide heating to an exterior wall of a space and provide displacement ventilation air to the occupied area of the space.
Representative of the art is U.S. Publication No. 2012/0270494 which discloses an induction-displacement neutral wall air terminal unit includes a housing defining a supply airflow path, a connected return airflow path, and a heating airflow path separated from the supply and return airflow paths by at least one interior wall. The unit also includes a plurality of induction-type nozzles located within the supply airflow path, that are deliver a ventilation air flow stream into the supply air flow path. The nozzles induce a return air flow stream through the return air flow path that mixes with the ventilation air flow stream to form a supply air flow stream delivered to a supply air outlet. A heating element is disposed within the heating airflow path to heat air within the heating air flow path. A plurality of fans may be placed within the heating airflow path to increase the overall heating capacity of the unit.
What is needed is an induction displacement unit comprising an induction plenum communicating with a first discharge plenum and a second discharge plenum, the first discharge plenum in communication with a heating coil and the second discharge plenum in communication with a cooling coil. The present invention meets this need.
The primary aspect of the invention is to provide an induction displacement unit comprising an induction plenum communicating with a first discharge plenum and a second discharge plenum, the first discharge plenum in communication with a heating coil and the second discharge plenum in communication with a cooling coil.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises an induction displacement unit comprising an induction plenum comprising a plurality of first nozzles communicating with a first discharge plenum and a plurality of second nozzles communicating with a second discharge plenum, a return air plenum, a heating coil disposed between the return air plenum and the first discharge plenum, a cooling coil disposed between the return air plenum and the second discharge plenum, the induction plenum vertically disposed between the heating coil and the cooling coil, the heating coil disposed in an upper portion of the unit, the first discharge plenum disposed to induce a substantially vertical discharge, and the second discharge plenum disposed to induce a substantially horizontal discharge.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.
Wall displacement unit 100 comprises an induction plenum 11 and a coil for air heating 12 and a coil for air cooling 13. Induction plenum 11 is vertically disposed between the heating coil 12 and the cooling coil 13 in a stacked arrangement. Heating coil 12 is vertically disposed in an upper portion of the unit while the cooling coil 13 is disposed below the elevation of the hearting coil 12. This vertical configuration takes advantage of the buoyant (lower density) nature of warmer air when compared to cooler air. Induction plenum 11 further comprises a plurality of air injection nozzles 14, 15 in communication with discharge plenum 20 and discharge plenum 18 respectively.
Air from the induction plenum 11 flows through nozzles 14, 15 thereby inducing a return flow of room air from the conditioned room (R) into the return air plenum 16. A portion of the returned room air flows through cooling coil 13 thereby reconditioning the return room air prior to mixing with the primary air jets in the lower discharge plenum 18. The return air is then discharged at low velocity as supply air through the lower part of the perforated front cover, 17 and 17A, in a substantially horizontal direction when in cooling mode operation.
In heating mode operation, the supply air discharged through the lower part of the front cover 17, see 17A, delivers prime ventilation air at near room temperature. The main source for heat load neutralization of a cold outside wall or window 19 is the upper heating coil 12. The returned room air flows through heating coil 12 to recondition the room air prior to discharge through grille 21. The reconditioned room air is then mixed with the primary air jets from nozzles 14 in the upper discharge plenum 20. Nozzles 14 discharge in a generally upward direction. Nozzles 15 discharge in a generally downward direction. Discharge plenum 20 is in an upper portion of the unit so as to facilitate an upward or substantially vertical air flow.
Heating coil 12, disposed in an uppermost portion of the unit, heats the air and when mixed with the air flow from nozzles 14 elevates the temperature of the return air entering the coil from the return plenum 16, thereby causing forced convection. Heated air is discharged upward through the grill 21 on top of the unit. Upon exiting grille 21 the heated air rises along the perimeter wall 19 and window 22 to create a building heating load neutralizing warm air curtain.
Each unit can be sized to fit under a sill adjacent to the perimeter wall 19 mounted to the floor 23 or wall 19. The unit provides spacing for connecting hardware 24 on both sides of the unit inside the housing. Although the unit is designed for use in new buildings, it can also be used for refurbishing existing high-pressure induction systems.
Unit 100 further comprises water control valves 26, 27. Valve 26 controls hot water flow from a boiler (not shown) to the heating coil 12. Valve 27 controls cold water flow from a chiller (not shown) to the cooling coil 13. A thermostat (not shown) in the conditioned space controls the room temperature by controlling operation of the water circuits entering the coils through the water control valves 26, 27. The heating and cooling coils may be controlled by either a two-way water valves 26, 27 or alternatively with three-way water valves.
In this embodiment the inlet air flow is received into the unit through the front of the unit 17. A portion of the inlet flow is diverted through the heating coil 12 and a portion through the cooling coil 13. In particular, since heating coil 12 and cooling coil 13 are immediately adjacent the induction plenum the primary air discharged from the induction plenum 11 through nozzles 14, 15 is efficiently used to induce an air flow for both heating 31 through heating coil 12 and for cooling 29 through cooling coil 13. This configuration does not require fans to move the air through the unit.
The mass flow of the discharged heating supply air can be adjusted by the quantity of nozzles 14 dedicated to heating. The air curtain created by discharge 31 in front of a window or cold wall is configured to roll the air within the adjacent area of the perimeter wall, and not to disturb the stratification created by the displacement ventilation. The mass flow, and therefore the quantity of nozzles 14 dedicated to heating, can be customized to accommodate 120° F., 140° F. and 180° F. water entering from a boiler (not shown).
Cooling coil 13 is not operating during the heating season, but prime air pressurizing at approximately 0.25″ to 1.0″ w.g. induction nozzles 15 causes the return air 30B to be drawn through the cooling coil 13. Return air leaving the cooling coil, at approximately 72° F., will mix with the conditioned prime air at approximately 65° F. The mixed air 32 at approximately 68° F. is discharged through the lower discharge plenum 18 in a substantially horizontal direction.
The unit provides at least 8,000 btuh of heating through the heating airflow path when the heating coil 12 is served by hot water having a temperature of approximately 180° F. The unit can be configured to operate in a heating mode wherein the heating coil 12 provides heated air through the heating airflow path; and a ventilation mode wherein the unit provides a supply airflow stream having a temperature of about 53° F. The heating mode can be simultaneously activated with a ventilation mode.
The number and diameter of nozzles 14 can be selected based upon the temperature of the water entering the heating coil 12. The numeric values included in this description are not intended to limit the scope of the invention and are provided as examples only.
Assuming a total of 42 nozzles (14), the diameters are:
Assuming a nozzle diameter of 0.188 inches the nozzle quantities are:
In operation, the inventive unit creates a simultaneous mixing heating curtain neutralizing cold perimeter loads while utilizing displacement ventilation for the inner occupied space. The inventive induction displacement wall unit also meets the noise requirements of ANSI Standard S12.60, which is advantageous in applications where reduced noise is desirable, such as in school classrooms.
In operation the unit provides a method of conditioning a space using an induction displacement unit. The unit induces a return air flow into the unit by discharging pressurized air within the unit. The return air flow stream comprises a single stream of air entering the unit through the front of the unit. The unit induces a portion of the return air flow stream 28 to flow through a heating coil and induces a portion of the return air flow stream 28B to flow through a cooling coil. The unit discharges the air flow from the heating coil in a substantially vertical direction. The unit discharges the air flow from the cooling coil in a substantially horizontal direction.
Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.
