Control of exhaust systems
Exhaust capture and containment are enhanced by means of automatic or manual side skirts, a sensitive breach detector based on interference effects, a combination of vertical and horizontal edge jets, and/or corner jets that are directed to the center diagonally from corners. Associated control functions are described.
1. A fume hood, comprising:
a hood portion connectable to an exhaust system and having a recess and a lower edge of the hood portion surrounding the recess,
the hood portion being configured to cover a fume source,
the recess having a vent through which fumes are drawn from the recess,
the vent being positioned on a rising side of the recess and covered by a grease filter,
the recess being configured to create a buffer zone to help insure that transient or fluctuating surges in a convection plume from fume source do not escape a steady exhaust flow through the vent; and
a jet generator located at said lower edge and configured to generate a combination of a first planar jet being relatively horizontal in direction and a second planar jet being relatively vertical in direction, said first planar jet being directed toward said hood portion recess, wherein
said first and second planar jets both extend continuously along the at least a forward section of said lower edge, and
the jet generator employs conditioned air as a source for generating said first and second planar jets, and
said first planar jet and said second planar jet emanate from a common plenum.
2. The fume hood according to claim 1 , wherein
an initial velocity of the first planar jet is between 2 and 3.5 times an initial velocity of the second planar jet.
3. The fume hood according to claim 1 , wherein
the first planar jet is directed directly into said hood portion recess.
4. The fume hood according to claim 1 , further comprising:
a wall, wherein the lower edge around the recess is a straight edge located opposite the wall.
5. The fume hood according to claim 1 , further comprising:
side skirts on lateral sides of the hood portion.
6. The fume hood according to claim 1 , wherein
said jet generator is further configured to generate a combination of said first and second planar jets at said recess lower edge on forward and lateral sections thereof such that the first and second planar jets surround the recess on at least three sides.
7. The fume hood according to claim 1 , wherein
said jet generator is further configured to generate a combination of said first and second planar jets at said recess lower edge on forward and lateral sections thereof such that the first planar jet on the forward section is directed perpendicular to the first planar jet on the lateral sections.
8. The fume hood according to claim 1 , wherein
said first and second planar jets are formed from coalesced individual jets generated by respective series of circular openings arranged along respective lines following said lower edge.
9. The fume hood of claim 1 , wherein
the positions of the first and second planar jets is such that the first planar jet is, at all points along said at least a forward section, proximate the second planar jet.
10. The fume hood of claim 1 , wherein said first and second planar jets extend continuously along said at least a forward section.
11. A fume hood, comprising:
a hood portion connectable to an exhaust system and having a recess and a lower edge of the hood portion surrounding the recess, the hood portion being configured to cover a fume source, the recess having a vent through which fumes are drawn from the recess, the vent being positioned on a rising side of the recess; and
a jet generator configured to generate a relatively horizontal planar jet along at least a forward section of said lower edge and directed toward said hood portion recess and to generate a relatively vertical planar jet along said at least a forward section, wherein
said relatively horizontal planar jet and said relatively vertical planar jet both extend at least along the same forward section of said lower edge, and
the jet generator employs conditioned air as a source for generating said relatively horizontal and relatively vertical planar jets.
12. The fume hood according to claim 11 , further comprising:
a grease filter positioned in the vent.
13. The fume hood according to claim 11 , wherein
initial velocity of the relatively horizontal planar jet is between 2 and 3.5 times initial velocity of the relatively vertical planar jet.
14. The fume hood according to claim 11 , wherein
said relatively horizontal and relatively vertical planar jets extend continuously along said at least a forward section.
15. The fume hood according to claim 1 , wherein
said jet generator is configured such that a flow volume of the first planar jet is between 3 and 15 ft 3 /min per linear foot of length of the lower edge along which the first planar jet extends.