Low Mixing Ventilation Jet

Abstract

A ventilation system with hardware to direct two independent airflows, wherein an outer airflow (at least partially) surrounds the an inner airflow. Preferably the inner and outer airflows come from different sources such that the air of the inner airflow has higher associated costs than the air of the outer airflow. For example, the inner airflow may be more cleaned and / or more thermally conditioned than the outer airflow. The inner airflow may have a different velocity than the outer airflow. Preferably, the ventilation system is a PVD, but other applications are also contemplated, such as: (i) spot-cooling; (ii) air curtains (for example for a refrigerated food section or case in a market); (iii) medical devices (for example, oxygen supply devices, “blankets” of thermally conditioned and / or cleaned air for infants, patients in surgery or burn victims, shields of cleaned air for protection against microbes for patients with compromised immune systems); (iv) personal humidifiers; (v) personal dehumidifiers; (vi) thermal and / or humidity control for plant or animal enclosures; and / or (vii) any other ventilation system for controlling at least one type of air characteristic (see Definitions section).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to ventilation systems and more particularly to ventilation systems for providing cleaned air (see Definitions section), thermally conditioned air (see Definitions section) and / or humidity-controlled air to a particular zone.[0003]2. Description of the Related Art[0004]It is often desirable to provide cleaned, thermally conditioned and / or humidity controlled air to a particular zone. As one example of this, research indicates that providing building occupants with devices to control the flow of air in their immediate environments to their personal preferences can enhance their satisfaction and work performance. A couple examples of such research are set forth in: (i) Arens, E., T. Xu, K. Miura, Z. Hui, M. Fountain, and F. Bauman (1998), “A study of occupant cooling by personally controlled air movement”, Energy and Buildings, vol. 27, pp. 45-49 (1998); (ii) Melikov, A. K., R. Cermak and M. ...

AI Technical Summary

Benefits of technology

[0015]The present invention relates to ventilation (see Definitions section) nozzles and new applications for ventilation nozzles. The ventilation nozzles of the present invention provide (at least) two airflows wherein on outer airflow (at least partially) surrounds an inner airflow. Preferably, the outer airflow has different temperature, humidity and / or cleaned air (see Definitions section) than the inner airflow, and is therefore less expensive to produce than the inner airflow. The outer airflow decreases the degree of jet mixing and entrainment of the inner airflow.

[0016]Through the use of present invention, higher BZ air quality and enhanced satisfaction can be achieved at no penalty in net energy consumption, or possibly even at a lower energy consumption for cleaning and / or thermal conditioning. This may be possible because the 15-20 cfm of clean air per person indicated in ASHRAE Standard 62 for acceptable indoor air quality (IAQ) is based on conventional mixing ventilation systems, which use the clean (fresh) air to dilute the concentration of indoor pollutants in the occupied spaces, thus producing acceptable air quality. As mentioned above in the discussion of Fanger, improvement in air quality beyond the acceptable level: (i) has a substantial positive affect on satisfaction and productivity, but (ii) requires a relatively large volumetric flow of clean air when prior art ventilation systems are used. This large volumetric flow has commensurately large energy costs associated with: (i) thermal conditioning; (ii) filtering / cleaning and / or (iii) moving the air. On the other hand, the present invention can provide similar levels of clean air to a user's BZ using a smaller volumetric flow having commensurately lower energy costs.

[0017]On the other hand, with the present invention, the PVD delivers the clean air of the inner airflow directly to the breathing zone with the help of the less-cleaned and / or thermally-conditioned outer airflow. An effective delivery system for the inner airflow requires only supply a fraction of the ASHRAE Standard amount of clean air required by whole room mixing ventilation systems. PVDs of the present invention can result in net energy savings and reduced inhalation exposure to indoor pollutants by reducing the entrainment of surrounding indoor pollutants in the PVD clean, inner airflow. Because the clean and / or thermally-conditioned inner airflow is relatively volumetrically small and delivered efficiently through space to the individual's breathing zone, the present invention may lead to net energy savings compared to both conventional centralized ventilation systems and conventional PVDs.

[0018]In ventilation systems according to the present invention, the outer airflow may, or may not, have a different velocity at the point of departure from the nozzle than the inner airflow. The inner and outer airflows are directed by the nozzle in at least substantially the same direction (that is, the airflow direction), but the inner and outer airflows may or may not leave the nozzle at the same location as measured along the airflow direction. Preferably the use of the outer airflow extends the length of the potential core of the inner airflow. Preferably, the use of the outer airflow will cause air to have characteristics (for example, temperature, humidity and / or cleaned air characteristics) more similar to that of the inner airflow at a greater distance from the nozzle.

[0020]The Definitions section defines the terms “air characteristic” and “air characteristic type.” In some embodiments of the present invention, the respective air supplies of the inner airflow and outer airflow may be controlled to make a smoother gradient, with respect to some air characteristic, across the combined cross section of the inner and outer airflows. For example, assume a first ventilation system according to the present invention where the inner airflow is cooled to ambient temperature minus X degrees (that is, A-X degrees), and the outer airflow is cooled to A-Y degrees. Further assume a second ventilation system according to the present invention that achieves identical cooling at the same distance from the nozzle, but where the outer airflow is not cooled at all (that is, outer airflow at temperature of A), and the inner airflow temperature is cooled to A-Z degrees, where X<Z and Y<Z. In some air cooling applications, it may be cheaper to use the first ventilation system where both the inner and outer airflows are somewhat cooled, in favor of the second ventilation system where only the inner airflow is cooled, albeit cooled to a greater degree. The first ventilation system, with its smoother temperature gradients across the airflow cross section may also be more comfortable for users.

Problems solved by technology

This large volumetric flow has commensurately large energy costs associated with: (i) thermal conditioning; (ii) filtering / cleaning and / or (iii) moving the air.

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