SE444609B - A regulatory device for defrosting of the cooler battery in a warm air exchanger pump - Google Patents

Abstract

A regulatory device for defrosting of the cooler battery (3) in a warm air exchanger pump (3,4,5,6). A circumvention passage (7), parallel to the cooler battery (3), has a sensor unit (8) for the measurement of the air flow in this passage, in which air flow varies depending on the degree of ice formation in the cooler battery. The sensor unit (8) consists of two temperature sensitive electronic components, one of which is electrically heated, and because of the cooling effect of the air flow, emits a signal which is substantially linear and air flow dependent. The differentiation (δU) between these signals is used for the control of the heat exchanger's operation so that the cooler battery is maintained at the lowest possible temperature without the kind of ice formation which restricts heat absorption.<IMAGE>

Description

IJI 15 20 25 30 8305668-9 2 device consisting of a heating coil arranged under the cooling coil in a vertical air shaft, in the upper part of which a fan is arranged, the air flowing upwards during heat transfer contact with the heating and cooling coils. As ice forms on the cooling coil, the pressure above the cooling coil drops, and this pressure drop is sensed by means of a temperature sensor in a suction pipe section arranged in the shaft wall between the cooling coil and the fan. Air is heated through this pipe section, which is heated by a heating coil. The heating of the air here depends on the air flow, and the greater the air flow, the lower the air temperature that the temperature sensor senses. A second temperature sensor is arranged outside the air shaft to compensate for the temperature variations in the ambient air. When the temperature difference between the two temperature sensors reaches a predetermined minimum value, a defrost cycle is initiated by switching on the heating battery (while simultaneously switching off the heat pump's compressor).

The main object of the present invention is to improve such a control device in such a way that the control accuracy is improved and the required defrosting can be achieved only by controlling the heat pump compressor, so that a special heating battery becomes unnecessary and the heat economy becomes even better. In addition, a simple design, low manufacturing cost and good functional reliability are sought.

As is apparent from the claims, these objects are achieved in that the preheated electronic component essentially consists of a diode or a transistor connected in a voltage divider in said bridge connection; wherein a control signal for the exhaust air heat pump is obtained directly as a result of a linear temperature and air flow dependent voltage variation.

The preheated component receives heat through direct heat transfer, mainly through heat conduction or heat! oo o oooo oo oooo oo I o o o o o o o o o o o o o o o o o o o o o o o o o o o o oo o o oo oo 8305668-9 3 radiation from the heat generating component, i.e. essentially without the transmission of the flowing air. The heat transfer can be effected from a nearby resistor, in particular close to a resistor, or the active temperature-sensitive electronic component can itself generate the heat during current passage. The by-flowing air in the bypass passage thus has only a cooling effect on the active component and no heat-transferring function. It is also essential that the reference component is arranged in the bypass passage itself (which is made possible by the air flow having no heat transfer function), whereby the compensation for all other varying parameters can be achieved and the air flow sensing can be refined. By this arrangement a linear sensing characteristic can also be obtained, even with rather simple and inexpensive electronic components, as will appear below. This enables very precise regulation, so that the heat pump can work optimally. A further advantage of the sensing components according to the invention is that they can be mounted in a single sensor unit, which is easy to install. Optionally, such a sensor unit can be combined with a bypass duct piece, so that a single installation unit is obtained.

A particularly simple electronic connection is obtained if the two electronic components are connected in separate voltage dividers in a bridge connection, whereby the measuring and reference signals can be taken out as voltage signals from resp. voltage divider. After amplification, the differential voltage signals can be applied to a voltage level sensor, e.g. a Schmitt trigger or the like, which in turn can control a heat pump's compressor actuating relay, so that the compressor operates intermittently with switching on at a first voltage level and switching off at a second (higher) level.

One or both voltage parts can contain a potentiometer, so that the switch-off and switch-on points can be adjusted as desired.

The invention is explained in more detail below with reference to bi k) UI 00 en 0 oo Q oo 0 Oona ons O 0 oo 'O .: OQO:: .O: a.' CI .C QIÛI O 'OOOQO.' ° ua 2. Ûpï-Ül. 8305668-9 4 accompanying drawing, which illustrates some preferred embodiments.

Fig. 1 schematically shows an exhaust air heat pump circuit and a pre-formation duct; Fig. 2 shows a block diagram of a control device according to the invention; Fig. 3 schematically shows an electrical sensing device in the form of a bridge coupling; Figs. 4A-4D show four different embodiments of the bridge coupling according to Fig. 3.

Fig. 1 shows an exhaust air duct 1 included in a building's ventilation system. Upstream of an exhaust air fan 2, a cooling battery 3 is inserted to extract heat energy from the outflowing ventilation air. The cooling coil 3 consists of an evaporator in a closed heat pump circuit comprising a compressor 4, a condenser 5 (from which heat is returned to the building, for example via radiators, to a hot water tank or to an accumulation tank) and a throttle valve 6. A bypass channel. 7 is drawn parallel past the cooling coil 3 to bypass a small part of the air flow. In the duct 7, an air flow sensing electric sensor 8 is inserted, which emits an electrical signal proportional to the air flow in the duct 7.

This signal is directly dependent on any stress or icing on the heat-absorbing surfaces of the cooling coil, because such stress or icing leads to increased pressure drop and consequently stronger air flow in the bypass duct 7.

As can be seen from Fig. 2, the sensor 8 is connected to an amplifier 9, which is connected to a level sensor 10, e.g. and Schmitt trigger. The level sensor 10 controls a relay 11, which acts on the heat pump's compressor 4, as discussed above. According to the invention, the sensor 8 consists essentially of two electrical devices, schematically in Fig. 3.

One component K1 serving as a measuring sensor is electrically preheated and emits a voltage signal U1 depending on the cooling in the exhaust air flow, while the other component K2 serving as a reference sensor is connected in parallel in the bridge connection and emits a reference voltage signal U2. The difference -Å U between the voltage signals U1 and U2 constitutes the compensated '- electronic components K1 and K as shown in the measurement signal and forms the basis for the control according to Fig.2.

As indicated in Fig. 1, the components K1 and X2 are arranged fairly close to each other in the bypass passage 7, but at such a mutual distance that the preheating does not directly affect the component K2 by heat conduction or heat radiation. The preheating of the component K1 can mean the heating of the by-passing air duct.

The embodiment of the sensor circuit shown in Fig. 4A comprises two parallel voltage dividers, namely a first voltage divider with a trim potentiometer R1 and a biased silicon diode D1, and a second voltage divider with a resistor R2 and a similarly biased silicon diode D2 of the same type as D1. The silicon diode D1 is preheated by a parallel-connected, low-impedance resistor RV. The heat transfer takes place partly through radiation and partly through heat conduction (via the electrical conductor connection as well as through the respective component housing). Under the influence of the air flow, the diode D1 cools, giving a voltage variation of approx. 2mV / ° C. The diode D2, on the other hand, maintains essentially the same temperature as the flowing air, and the difference AXU I UI-U2 therefore becomes strictly dependent on the air flow alone.

Fig. 48 shows a variant with reverse voltage zener diodes D'1, D'2 in resp. voltage divider. In this case, the resistances R1 and R2 of the resistors are so adapted that D'1 conducts a current in the reverse direction which provides the required heating. Thus, no separate, heat-generating resistor is needed in this embodiment. This also applies to the embodiment according to Fig. 4C, where a transistor T of 8305668-9 e is correspondingly heated during current passage. In this case, trim potentiometers (R3 and R2, respectively) are inserted in both voltage parts for fixing the transistor current operating position or resting point. At this resting point, the transistor T has a given internal output loss power, which produces the desired heating. The base-emitter junction is then biased and gives a corresponding voltage variation (approx. 2mv / ° C) as the diode D1 in Fig. 4A. The voltage U1 is therefore taken out via this base-emitter junction, while the reference voltage U2 is taken out via the diode D'2. The emitter of the transistor T and the cathode of the diode D "2 are interconnected to provide a stable common signal ground.

Fig. 4D finally shows an embodiment with high-quality temperature sensors 81 resp. S2, which has particularly good linearity (eg of type Analog Device AD 590). This embodiment, which like Fig. 1 has a separate, heat-generating resistor Rv, can be used e.g. for trimming and testing purposes.

The invention can be applied in various ways within the scope of the patent claims. For example, the signals from the sensor components K1 and K2 can control the heat pump circuit in other ways than by switching the heat pump compressor on and off, namely by continuously controlling the compressor power or connecting one or more parallel working heat pump circuits with a common cooling coil. In this way, even more precise regulation can be achieved, so that the degree of stress or ice formation can be kept at an optimal, constant level that ensures the best possible heat exchange.

Claims (5)

8305668-9 PATENT REQUIREMENTS Control device for defrosting cooling coil direction (3) in an exhaust air heat pump (3,4,5,6), comprising a bypass passage (7) arranged in parallel with the cooling battery with means (8) for sensing air flow variations in this passage due to icing in the cooling coil, which sensing means (8) comprise a temperature-sensitive, preheated electronic component (K1) arranged in the bypass passage (7) connected in a bridge connection, characterized in that said preheated electronic component essentially consists of a diode (D1, Then) or a transistor connected in a voltage divider (AD) in said bridge connection (Fig. 3.4), whereby a control signal (ÅÄU) for the exhaust air heat pump is obtained directly as a result of a linear temperature and air flow-dependent voltage variation. Device according to claim 1, characterized in that said preheated electronic component (D1x S1) is supplied with heat from a nearby resistor (Rv), which directly transfers heat mainly by heat conduction and heat radiation (Figs. 4A, 4D). Device according to claim 1, characterized in that said preheated electronic component (Di: T) consists of a heat-generating component during an oncoming passage (Fig. 4D, Fig. 4C). Device according to Claim 3, characterized in that the heat-generating component consists of a reverse voltage zener diode (Di) (Fig. 4B). Device according to any one of claims 1-4, characterized in that said control signal (ÄXU) is amplified in an amplifier (9), to which is connected a voltage level sensor (10), which in turn controls a the compressor (4) of the heat pump circuit actuating relay (11), so that the compressor operates intermittently with switch-on at a first voltage level and switch-off at a second voltage level, in