Background of the invention The primary function of an air treatment apparatus is to provide a building and the people working and staying there with fresh air and to remove polluted, "odorous"air. The dimensioning is made due to flow volume at the density 1.2 kg/m3 (atmosphere pressure 101325 Pa, temperature 20°C, and relative humidity, RH, 40%), daily called the airflow. The fresh airflow is being tempered differently at different seasons and contributes to the thermo climate in the building. Further, sometimes functional parts are added regulating the humidity of the air and thereby the building. The main part of the air treatment apparatuses used in Northern Europe are provided with a heat recovery system to reduce energy consumption and the maximum effect need required to heat, and cool, respectively, the fresh air. Primarily three types of heat exchangers are used, viz. rotating heat exchangers, plate heat exchangers and battery heat exchangers.

Rotating heat exchangers have the highest temperature recovery yield, 75 to 85 %, dependent on manufacturer. At normal use there is no risk of freezing onto the rotating heat exchanger but the efficiency is maintained even during the coldest days of the year. The heat exchanger also works efficient at cool recovery. The drawback is a risk for transferring odors. A rotating heat exchanger should thus not be used for ventilation of buildings having different productivities, such as offices and workshops, when a transfer of odor is made from the"dirtier" to the"cleaner"work place. Rotating heat exchangers can however, be used for each work place per se in such a building, but then request separated ventilation

systems. In a place in mid-Sweden having a normal temperature of 5, 8°C over the year (Skara, Västergötland) and lowest dimensioning out door temperature of - 20°C the effect requirement for after heating be reduced from 47 kW without heat exchange to 5,7 kW using a rotating heat exchanger, per m3/s. The energy consumption for after heating is, in the same calculation, 140 MWh/year without heat recovery and 8 MWh/year using a rotating heat exchanger.

Plate heat exchanger has a normal temperature efficiency of about 60 %. The construction gives the largest risk for freezing on of the said types of heat exchangers. The outlet air channel closest to the outdoor air inlet is subjected to cool outdoor air. The heat exchanger has, at a correct construction, adaptation and mounting a small risk for odor transfer.

Battery heat exchangers are dimensioned for a temperature efficiency of between 50 and 60 %. The risk for freezing on is small. By separating the apparatus with regard to inlet air and outlet air all risk for odor transfer is eliminated.

In an installation of an air treatment apparatus the effect requirement of the fan/fan system of the air treatment apparatus with the airflow taken three times.

Adjusting the airflow with 10 % means a 33 % higher effect requirement and additionally an increased energy requirement of the heating system and the cooling system, respectively, to reach the correct temperature in the building. An incorrect inlet airflow has a direct influence on energy requirement for regulating the temperature. In cases of heat recovery one normally strives for a balance between inlet and outlet airflows. Both a too small as well as a too large outlet air flow increase the energy requirement to reach a correct temperature in the building. If the outlet airflow is too high the infiltration of outdoor air increases corresponding to the flow unbalance. As the airflow is the primary issue in an air treatment system then a too small an airflow is negative both to the building and the people staying there. It is thus extremely important that the airflow is correct.

More and more manufacturers of air treatment apparatuses have developed systems for monitoring airflow in the apparatuses. In the beginning separate measuring modules were developed. In order not to create great pressure drops one had to be satisfied using a monitoring pressure of less than 100 Pa. During the latest years the flow monitoring has been concentrated to the fan/fan system of the air treatment apparatus.

US-A1-2001/0007337 discloses a process and a system for controlling the mass flow in an air craft by means of a continuous recalculation of efficiency characteristics in a closed calculation system, whereby regard is taken to the pressure in the pipe system, temperature, flow volume and height above ground level. In the system there is used an air conditioning system which provides predetermined values of inlet air with regard to in particular the temperature.

Control with regard to outlet temperature is lacking in such a control system to monitor the mass flow.

US-A-5,341, 988 relates to a wireless air balancing system for the treatment of air in a space, such as an office space via an air conditioning apparatus arranged in said space. It is here not a question of pure air treatment apparatuses for buildings but of simple spaces where a simple air conditioning is required with regard to flow and air temperature in the space.

US-A-3,192, 848 relates to an air directing system in aircrafts, and in particular for adding so called bleed air to an aircraft from an inlet line in a jet aircraft. Flow sensors in said inlet lines control the system. This patent is not related to mass flow control at the air treatment apparatus but a mere control of the inlet air to add the amount of air needed under particular conditions.

SE-C-500 361 relates to a circulation apparatus and does not relate to an air treatment system. The problem to this technical solution is to obtain a larger or smaller surface of impact of the fan depending on the temperature, i. e. , to increase the speed of the fan if the temperature should increase in a space. Thus no control with regard to mass flow and a varying outdoor temperature takes place.

Summary of the present invention Using different control and regulating technical solutions lots of energy can be saved. Common to such solutions are that one adapts the air flow from a requirement point of view at e. g. , pressure control which is used when different<BR> part systems shall be able to be closed off (e. g. , in spaces which are not used, for elimination of odors in the system, and other things) without affecting the air flow

to the rest of the spaces, and so that the pressure of the main channel of the air treatment system is kept constant.

Detailed description of the present invention The present invention relates primarily to an air treatment apparatus which is controlled by a control and regulating system and contains at least one fan, where the outdoor temperature at the inlet of the outlet air fan varies, whereby the air treatment apparatus comprises at least one temperature sensor for the registration of actual outdoor temperature, the temperature efficiency of the heat exchanger is known, the air treatment apparatus contains at least one registration and calculation unit which determines the mass flow through the outlet air fan to a predetermined value, and the registration and calculation unit controls the airflow of the outlet air fan via a control means so that this predetermined value is obtained.

In the attached drawing an air treatment system in a fan house 1 is schematically shown comprising an inlet air fan 2 provided with air flow measurement and revolution control and an air outlet fan 3 with air flow measurement and revolution control. In the fan house 1 in connection with a channel 4 for inlet air there are temperature sensor 5 for measuring and transferring outdoor temperature. The values from the outdoor temperature sensor 5 are transferred to a control and regulation unit 6 including a registration and calculation unit. The control and regulation unit 6 hereby controls the inlet airflow qt and the outlet air flow qf, which flows pass a rotating heat exchanger 7. Control means 8 for regulating the air flows to and fro are given schematically.

In a simple set up including one fan and one channel system the volume flow measured in m3/s constant independent of the temperature at the inlet of the fan.

A change of the temperature means, however, that the density of the air changes and thereby will the mass flow in kg/s become changed. If one starts from +20°C which is the temperature at normal dimensioning to-20°C it means that the density of the air and thereby the mass flow and the effect requirement of the fan will increase with about 16 %.

Fans, which are so placed that the temperature varies over the changes of the seasons, will obtain a varying mass flow. Examples of such fans in air treatment apparatuses are outlet air fans placed after an inlet heat exchanger and then in

particular after a rotating heat exchanger, which has the highest temperature yield. Another example is an inlet air fan placed in front of an optional after heating battery. However, the variation of mass flow will be reduced considerably if a heat exchanger having a high temperature yield is placed in the outdoor air prior to the fan.

In air treatment systems the mass flow will e constant in each cross section if one disregard any leakage. If the temperature of the air changes in a cross section the density of the air will be changed and the volume flow thereby, as well. An installation having differences in temperature has, with other words, different air flow (volume flow) in different cross sections. Traditionally, fans have been placed in such a way that the temperature in the inlet of the fan is constant which also leads to constant volume and mass flow in the installation. There are, however, exceptions as the outlet air fan is normally placed after an optional heat exchanger. The outlet air flow will thereby vary with great energy losses as a consequence, both as running energy to the fan and as energy to reach correct temp in the building. The consciousness of this relationship seems, however, to be small or even non-existing.

If it is supposed that in a specification it is set an inlet and outlet airflow of 1 m3/s, said volume flow is required at the density 1.2 kg/m3. If the outlet air temperature is set to 20°C, dimensioning outdoor temperature to-20°C, and the temperature yield of the heat exchanger is 80 %, it is obtained at the calculation, at lowest dimensioning outdoor temperature, a temperature of the outlet air after the heat exchanger, at the fan inlet, of-12°C, and the density 1.35 kg/m3. This leads to a volume flow of 1.12 m3/s having the density 1.2 kg/m3 at the outlet air opening if one disregards changes in pressure drops. The effect requirement of the fan will then, at running point, increase with 12 % and the heating system of the building will be loaded with 5.9 kW extra due to the increased infiltration of outdoor air.

The present invention thus relates to a combination of technical progress in a control and regulating soft ware to facilitate a desired volume flow having the density 1.2 kg/m3 (mass flow) in an air stream. Using the electronics of today reliability can be achieved as well as an acceptable cost level when it comes to a control and regulating equipment for frequency control with the intention to control e. g. , the revolution speed of a fan and for a control and regulating

equipment which moreover can be construed and be simply adapted to new functions depending upon need.

Within measuring technology pressure and temperature sensors been further developed and have fan and system manufacturers developed reliable systems for measuring of volume flow. Bases for being able to obtain control of an air treatment apparatus are thus present.

Measurement of airflow would be possible to carry in one plane where the variation of the temperature is minimal. This measurement can then form a base for controlling the airflow. In order to obtain accuracy long term stable, advanced flow monitoring means are required. Such flow monitoring means will, however, lead to unacceptable pressure drops, which increase the effect requirement of the fan present and normally there is lack of space in the apparatuses for a correct installation.

In an air treatment apparatus one or more temperatures are measured by temperature sensors placed in the apparatus, in particular in the inlet part of the fan (-s) present in the apparatus. The temperature sensors are placed close to the inlet (-s) of the fan (-s) or in such a way that the temperature at the inlet of the fan can be calculated with an acceptable accuracy (3°C or less, which leads to 1 % or less influence on the air flow). For example, the outdoor and outlet air temperatures and the temperature yield of a heat exchanger are the bases for the calculation of the temperature at the inlet opening of an outlet fan, which is placed after a heat exchanger. The temperature can, via a calculation be used directly to obtain a regulation to a desired mass flow, but to guarantee the correct flow there is often a flow measurement required. Such a measurement takes normally place by indirect measurement of a pressure, which is then converted to flow. The measurement of the pressure must thereby become temperature corrected before an actual airflow can be calculated.

A desired airflow at the inlet of the fan is calculated in accordance with the present invention by temperature compensating the dimensioning airflow so that a constant mass flow is obtained. In a control and regulating system all measurements and calculations and regulation of the airflow are carried out via an outgoing signal to a suitable regulating means. The flow can be regulated, e. g. , by means of throttle regulation but the most energy efficient way is the

regulate the revolution speed of the fan (-s) via a control of the frequency, which is also a preferred embodiment.

Thus, the present invention obtains an air treatment apparatus which is controlled by a control and regulating system and contains at least one fan, where the temperature at the inlet of the fan varies, whereby the air treatment apparatus contains at least one temperature sensor for the registration of actual temperature, the air treatment apparatus contains a registration and calculation unit which determines the mass flow through the fan to a predetermined value, and said registration and calculation unit, via a regulating means, regulates the air flow of the fan so that this predetermined value is obtained.

Registration of the temperature via the temperature sensors can be made at short or long time period intervals, but during stable weather and surrounding conditions it is considered suitable to have a registration done every minute up to every 10 minutes. When the registration shall be done is determined by the registration and calculation unit, whereby this can contain soft ware for determination of registration frequency, which one or more soft wares are based on the size and the velocity of the changes. If, e. g. , rapid temperature drops should occur control of the airflow might be done 2 times a minute, whereby thus registration must be carried out 2 times per minute as well.

According to a preferred embodiment of the present invention the air treatment apparatus comprises furthermore a means for air flow measurement, which is provided to give an outgoing signal to the registration and calculation unit for checking a set air flow.

According to another preferred embodiment of the present invention the means for air flow measurement is a pressure measuring means.

According to a further, preferred embodiment of the present invention the means for measuring airflow arranged at inlet part of the fan present in the air treatment apparatus.

According to a further other preferred embodiment of the present invention the regulation means is arranged to influence the air flow by means of a frequency control of the revolution speed of the outlet fan present in the air treatment apparatus.

According to another further preferred embodiment of the present invention the regulation means is arranged to influence the airflow by means of control of guiding rails present in the inlet of the fan house for the regulation of the rotation of the inlet air.

According to further preferred embodiment of the present invention the regulation means is arranged to influence the angle of the fan blades of axial fans for the regulation of airflow.

According to preferred embodiment of the present invention the regulation means is arranged to influence the airflow by means of influencing a throttling of the amount of inlet air to the fan (-s) present in the air treatment apparatus.

According to another preferred embodiment of the present invention the heat exchanger is a rotating heat exchanger, a plate heat exchanger or a battery heat exchanger.

According to another preferred embodiment of the present invention the air treatment apparatus further comprises a means for measurement of relative and absolute humidity, which means is arranged to provide an outgoing signal to the registration and calculation unit for control of the humidity in inlet air to said at least one fan.

According to a further other preferred embodiment of the present invention the air treatment apparatus is furthermore provided with a smoke detector arranged to provide a signal to the registration and calculation unit in order to prevent spreading of smoke coming from outside into the building. Later times larger fires in connection with densely populated areas has shown the problem with spreading of fire smoke which in some cases has contained toxic substances.

According to another preferred embodiment of the present invention at least one sensor is provided with equipment for wire less communication using a transmitter-receiver unit arranged to the registration and calculation unit.

According to a further preferred embodiment of the present invention at least one fan present in the air treatment apparatus is provided with equipment for wireless communication using a transmitter-receiver unit arranged to the registration and

calculation unit and arranged to receive control information for the regulation of the transporting air flow of the fan. A transmitter-receiver unit can be based on wireless or wired communication whereby wireless communication can be maintained by means of IR waves, radio signals, or hearable or unhearable sound waves.

Further, the present invention relates to a registration and calculation unit for air treatment apparatus and comprising at least one inlet unit for receiving of measured values from at least one sensor, comprising a calculation unit for the calculation of air flow values based on values received from the sensor, and at least one outgoing unit for the regulation of the air flow by means of an outlet fan present in the air treatment apparatus which fan is controlled to provide such a calculated air flow value. By means of this aspect of the invention it is obtained that all calculations and controls can be made immediately at occurred changes of the temperature in ingoing air to the inlet and/or outlet fans (-s) in the air treatment apparatus.

According to a preferred embodiment of this aspect of the present invention the calculation and registration unit encompasses a computer unit, such as in the form of a microprocessor with soft ware for the calculation of air flows based on values received from said at least one sensor.

According to a further, preferred embodiment of the present invention the registration and calculation unit comprises a transmitter-receiver unit for receiving of calculation values via a wireless communication for the calculation of air flows, transmittance of control signals for the regulation of the transported air flow of at least one fan present in the air treatment apparatus.

According to another aspect of the present invention it comprises a medium with information to be used in a registration and calculation unit, whereby the medium contains calculation bases in digital form for the calculation of air flows based on the construction specifications of a given air treatment apparatus. Hereby, the calculation bases can be changed in a simple way with regard to changes of the air treatment apparatus, expansion of a building, larger load of the building, and other factors influencing the basic specification for the air treatment as such.

According to a preferred embodiment of the medium of the present invention it consists of a disc provided with digital information, which disc can be read by the registration and calculation unit and information can be stored in said unit.

According to another preferred embodiment of the present invention the medium can be a CD-ROM or DVD disc with digital information, which can be read by the registration and calculation unit, and information can be stored in said unit.

According to a further aspect of the present invention it is a process for control of the mass flow in an air treatment apparatus, whereby at least one temperature of inlet air to at least one fan present in said air treatment apparatus is determined, that said temperature is the inlet signal for a calculation, said calculation is used for control of the mass flow through said at least one fan.

According to a preferred embodiment of the present invention, furthermore, the airflow is measured and the function for control is secured in such a way.

According to another preferred embodiment of this aspect of the present invention the airflow is measured via pressure measurement.

According to a further preferred embodiment of the present invention the airflow is measured at the inlet of said at least one fan.

According to another further preferred embodiment of the present invention the air flow is regulated by means of frequency control of the said at least one fan.