DE3030778A1 - Stale air heat recovery heat exchanger - has stale and external air by=pass valves, operated separately - Google Patents

Abstract

The heat exchanger has heat pipes mounted in a horizontal, inclined or vertical position in a frame, recovering heat from the warm stale air and an air conditioning system. A bypass flap valve (8,9) is mounted in the frame (2) on the stale air side (4.2.) and on the external air side (4.1) of the heat exchanger (4). These valves are individually adjustable, and they can be coaxial, one being mounted on a solid shaft and the other on a hollow one. In order to defrost the stale air side by raising the surface temps. of the pipes on this side above 0 deg.C, the external air valve (8) can be opened while the stale air one (9) is shut. If the external air temp. is equal to or greater than the stale air temp. minus 3 deg. C both valves can be opened.

Description

Letter from Blaa ^ ^ J Dipl.-Ing. G. Schliebs

to the German Patent Office., Munich Patent Attorney

The invention relates to a heat exchanger with heat pipes in the horizontal, inclined or vertical position in are arranged in a frame for the recovery of energy from warm exhaust air flows in ventilation systems.

Heat pipes are a device for transporting heat energy from a heat-emitting to a heat-absorbing mass flow. Inside a vacuum-tight closed In the tube there is a liquid that evaporates on the warm half and condenses on it the cold half of the pipe constantly transfers heat from one side to the other. A slight slope of this Pipes towards the warm end support the reflux of this condensate by gravity, so that the optimum effect is achieved.

When heat pipe heat exchangers are installed in air conditioning systems, moisture is then excreted on the outer surfaces of the heat pipes on the exhaust air side (warm side) if the dew point of the exhaust air is higher than the surface temperature of the heat pipes, which in certain operating states with very cold outside air (below - 15 ° C) can also be below ^{0 ° C.} The accumulation of frost or ice that occurs during this process must be defrosted periodically, as otherwise the air flow would be interrupted by the heat exchanger becoming overgrown with ice.

According to the prior art, defrosting is carried out by an air flap in the outside air duct in the direction of flow in front of the The outside air part of the heat exchanger reaches in combination *) in an air bypass, which the outside air when the Outside air part leads past the heat exchanger. This outside air

^:) with an air damper

Letter from BI&U k Dipl.-Ing. G. Schliebs

to the German Patent Office, Munich Patent Attorney

then, since the heat exchanger no longer heats the outside air, it must have an additional preheater be heated.

The exhaust air side can defrost, because when the outside air side is shut off, the surface temperature ^{will rise above O 0} C and the ice will defrost. This arrangement requires additional space for the bypass, which must be connected separately via air ducts. The inevitably unfavorable flow conditions result in additional air resistance. The air-side resistance of the heat exchanger on the exhaust air side is available throughout the year, combined with the corresponding energy requirement for the fan. The preheater required requires the most expensive peak load energy, as icing will occur especially on the coldest days.

The invention is therefore based on the object of finding an arrangement with which these disadvantages can be avoided and the energy balance is improved above the annual average.

This object is achieved in that in the frame of the heat exchanger on the exhaust air side and a bypass damper on the outside air side of the heat exchanger are arranged, which are individually adjustable. The two flaps, which in the open position inside the Release a bypass for the respective air flow in the heat exchanger, can be set individually. These are In an advantageous simple arrangement, the two flaps are arranged coaxially, and one flap is through one shaft, the other flap is adjustable by a hollow shaft seated on the same axis.

130067 / Öm

Letter from Blau Jy £ ~ Dipl.-Ing. G. Schliebs

to the German Patent Office, Munich Patent Attorney

According to the invention, not only the defrosting on days with ice accumulation is effected without additional structural effort on the ventilation system, but in particular the flow resistance of the outside air and exhaust air side of the heat exchanger on the days of the year (approx. 30 % = 3000 hours per year) on which a heat recovery is not necessary or is not economical due to the small temperature difference between outside air and exhaust air. ''
. . .- ■■ · '-

The invention and its advantages are explained below using examples. In the drawing show:

1-3 the three basic types of air flow in ventilation systems;

4 shows a longitudinal section through a heat pipe heat exchanger and

FIG. 5 shows a partial cross section through the heat exchanger according to FIG. 4; FIG. Fig. 6 on an enlarged scale storage and actuation the flaps of the heat exchanger.

In Fig. 1 are the exhaust air duct leading the warm air flow 1 arranged below and the outside air duct 3 leading the cold air flow above; the heat pipes in frame 2 of the Heat exchanger 4 are vertical.

FIG. 2 shows channels 1, which are led horizontally next to one another, for the exhaust air and exhaust air flows; the heat pipes are in frame 2 horizontally, with a slight inclination, arranged one above the other.

130067/048 *

Letter from BI = U fyS / Dipl.-Ing. G. Schliebs

the German Patent Office, Munich Patent Attorney

Fig. 3 shows channels 1, 3 that are run vertically next to one another for the air currents; here, too, the heat pipes are essentially horizontal, but side by side.

4 and 5 show the heat exchanger 4 open or in a longitudinal section, and the two can be seen in the frame 2 through a central wall 5 for the two air flows AL and FL separate compartments 4.1 and 4.2. The bundle of heat pipes 6 runs through both compartments, but does not take the whole cross-section of the heat exchanger. Rather, a lateral bypass is separated by a further partition 7, in each of which a (bypass) flap 8, 9 is arranged. The two bypass valves 8 and 9 are therefore next to the heat pipes 6 integrated into the frame 2 of the heat exchanger 4, so that the unit is built into the ventilation ducts 1, 3 can be done without additional space or assembly work on the construction site.

In Fig. 6, the bypass flaps 8 and 9 and their drive are shown in detail in FIG. In the (in the drawing) horizontal walls of the two bypasses are in ball bearings 10, 11 a hollow shaft 12 for the upper two-winged Flap 8 and guided in this a further shaft 14 for the lower flap 9 and mounted in a further ball bearing 13. On the protruding from the frame 2 stub shafts sit levers 15 and 16, with which the flaps accordingly the operating mode can be set.

The method for operating such a heat exchanger with heat pipes and integrated bypass flaps is characterized by that for defrosting an ice accumulation on the exhaust air side by heating the surface temperature of the heat pipes in the exhaust air above 0 ° C, the outside air damper 8 is opened while the exhaust air damper 9 is closed

130067/0484

Letter from Blaa

to the German Patent Office, Munich

Dipl.-tng. G. Schliebs

Patent attorney

remains and to reduce the pressure drop and thus energy loss over both parts of the heat exchanger in operating times with T _AT ^ (T ^ ₁ - - 3 C) both flaps 8, 9 are opened.

^L AL

FL

For the three typical operating states during the year, the two flaps are controlled as follows:

1. Winter operation

2. Transitional season and summer operation

3. Defrost control

8 and 9 are closed, the heat pipes 6 fully effective.

e.g. T. _T ^ (T

AL

^L FL

3 ° C), 8 and 9

opened, the air currents flow through the bypasses, hence in the heat exchanger only a small pressure drop, i.e. very little additional ventilation energy requirement .

8 is open, 9 closed, any frost build-up on the exhaust air side (when operating with room air humidification) thaws by heating the heat pipes 6.- Depending on the degree of ice build-up and the temperature and humidity conditions, the flap 8 can only be partially open .

From US Pat. No. 4,064,932 an arrangement is known in which the frame with the heat pipes can be rotated by means of a shaft lying in the central plane of the two channels, so that the transfer capacity of the heat exchanger and its flow rate change at the same time: with decreasing capacity Hull (with the frame rotated in the center plane) takes the

150067/0484

Letter from Blail Jg " . D Dipl.-Ing. G. Schüebs

^to the German Patent Office, Munich Patent Attorney

Bypass closed up to the full channel cross-section. This is supposed to also defrost an ice deposit, but this method is highly ineffective as both parameters are reciprocal linked and not individually selectable.

130067/0484

Claims (2)

Claims (Ii Heat exchangers with heat pipes, which are arranged in a frame in a horizontal, inclined or vertical position are, for the recovery of energy from warm exhaust air flows in ventilation systems, characterized that in the frame (2) on the exhaust air side (4.2) and on the outside air side (4.1) of the heat exchanger (4) a bypass valve (8, 9) is arranged, which individually are adjustable. 2. Heat exchanger according to claim 1, characterized in that the two flaps (8, 9) are arranged coaxially and one flap (9) by a shaft (14), the other flap (8) by a shaft seated on the same axis Hollow shaft (12) is adjustable. Letter from BIaI ₁ 2 Dipl.-Ing. G. Schliebs to the German Patent Office, Hünchen Patent Attorney 3t method for operating a heat exchanger with integrated bypass flap according to claim 1 or 2, characterized in that the outside air flap (8) is opened while the outgoing air flap is heated to thaw an ice build-up on the exhaust air side by heating the surface temperature of the heat pipes in the exhaust air above O ^{0 C (9) remains closed and both} caps (8, 9) are opened to reduce the pressure drop and thus energy loss over both parts of the heat exchanger in operating times init ^T AL "( ^T FL" ³ ° ^C ). 130067/0484 BATH ORIGINAL