DE19847504C1 - Fresh and recycled air volume control method for air-conditioning unit for automobile passenger space regulates ratio of fresh and recycled air volumes in dependence on detected air quality and required air temperature - Google Patents

Abstract

The air volume control method calculates a minimum fresh air volume in dependence on a limit value for the concentration of exhaust gases in the passenger space and calculates the temperature of the air to be supplied to the passenger space in dependence on the difference between the actual and the required air temperature, to determine the heating requirement, used for regulating the volumetric ratio of fresh air and recycled air.

Description

The invention relates to a method for controlling outside air and recirculating air volume flow in a ventilation system for the temperature of a room, especially in a vehicle for Passenger transport.

For economic and ecological reasons it is desirable, such systems with a possible operate low power input.

In the article by P. Bork, energy saving with the help of improved Automation concepts, in automation engineering practice atp, 1986, volume 28, number 4, pages 184-190 are air conditioning, which regulates both temperature and humidity, and energy saving driving for such a system described.

For reasons of hygiene, here a minimum external air content in the Be included supply air flow.

However, only qualitative rules for the operation of individual elements of the system such as mixing chamber, preheater, radiator, humidifier, etc. are given. Concrete information that allows to calculate an outside air volume flow or a power requirement for certain operating conditions is not available. In particular, the mixing chamber is operated only in two states, m _AVmin and m _AVmax .

In the article by U. Knau, air conditioning of the central car of the ICE the German Federal Railroad, published in Ki Klima-Kälte-Heizung 6/1990, Pages 270-273 an operating method is known in which a Outside air volume flow is fixed and as an energy source for heating and cooling serves.

DE 35 09 621 is a ventilation system with variable Volume flows and a method of operation known.

The plant is a two-channel system with one Cold air duct, in the fresh air via an air conditioner is fed, and a hot air duct, the heated circulating air leads.

Up to now, the following methods for controlling the systems are common in vehicles:

• 1. It is constantly promoted the proportion of outside air, the corresponding Design of the system for the maximum number of people in the room is required.
• 2. The proportion of outside air is adjusted in stages of occupation, without Consideration of the ratio outside / room temperature.
• 3. Regardless of the ratio outside / room temperature is the Supply air flow rate after the control deviation room temperature Setpoint / actual value set, without evaluation of the occupation regarding Indoor air quality. Examples are in the patents EP 0793 822 B1 and EP 0827 889 A3.
• 4. The concentration of gases in the outside air is measured and if increased concentration of a particular target gas occurs, the Supply of outside air is interrupted or in addition to this passed special filters. This is explained in EP 0713 454 B1.

All these methods do not use the two possibilities in a complex way

• - consideration of the number of persons or room air quality,
• Consistent utilization of the energy content of the outside air for the Temperature control of the room at certain partial load conditions (no Full occupancy, outside temperature 10.20 ° C), as in Central Europe too a majority of the operating time,

for energy-optimized operation of the systems.

The object of the invention is a control method for a to create a ventilation system that an operation with low energy consumption without Loss of comfort allowed.

The problem is solved by a method according to Claim 1.

Subclaims are directed to preferred embodiments.

Embodiments will be described below with reference to FIGS attached figures described. Show it:

Figure 1 is a schematic representation of a vehicle with a ventilation system for performing the method.

Fig. 2 is the supply air flow rate as a function of temperature Zulufttempe according to the method according to the invention;

Fig. 3.1 the required performance of the system as a function of the ratio of outside air to supply air volume

Fig. 3.2 shows the thermal performance of the system as a function of outside temperature and room load for various values of the outside air / supply air volume ratio; and

Fig. 4 is a flow chart of the method according to the invention.

The basis for the application of the method is an air treatment device, which contains the following units shown in FIG. 1 for the realization of the method:

• - outside air supply ( 1 )
• - recirculation air supply ( 2 )
• - supply air supply ( 3 )
• - organ for adjusting the air flow rates ( 4 )
• - Heating register ( 5 )
• - Cooling coil (optional) ( 6 )
• - Control device ( 7 )
• - facilities for recording the following quantities: ( 8 )
  outside temperature
  Room air temperature
  supply air temperature
  Occupation, ie number of people in the room or CO ₂ concentration in the room air

The plant with air as an energy source must be for the temperature of the Interior required amount of air with the appropriate temperature and Provide quality.

The basic connections are shown below and from this, the inventive method, which by controlling the Air volume flows the tasks mentioned with the least possible Energy use met, derived.

According to the occupation of the vehicle is to ensure a acceptable indoor air quality a certain delivery volume of outside air required. In addition, circulating air can be removed from the interior. Both volume flows are mixed, treated and as supply air the Interior supplied. This serves as an energy source. According to the Power requirements must be their temperature and the delivery volume in one certain relationship.

The condition of the room air indicates the need for the treatment of the supply air:

- Content of harmful gas - above limit: high proportion of outside air necessary - below limit: low proportion of outside air possible - temperature - above the setpoint: cooling demand - below the setpoint: heating demand

The required condition and the composition of the supply air shall be determined in accordance with Method, which is content of the invention, according to the two criteria Room air quality and thermal load determined.

Criterion 1

The indoor air quality results from the emission of pollutants in the interior, the outside air volume flow and that contained in the outside air Pollutants.

From the circumstances

• - closed room with certain outside and exhaust air flow rates
• - Ratio of outdoor / exhaust air volume flow = 1/1
• - Occupation of the room with persons, which per time unit one deliver certain volume of noxious gas
• - Outside air with a certain concentration of the same noxious gas
• - System in steady state is shown on the example of the noxious gas CO ₂ the relationship between pollutant concentration and outdoor air volume flow. Where:
  V _R - room volume in m ³ k _CO2R - concentration CO ₂ in the room in ppm AL = L <n _P - Number of people in the room V _CO2P - CO ₂ tax per person in m ³ / h V _Al - outdoor air volume flow in m ³ / h k _CO2A concentration CO _{2 of} the outside air in ppm V _CO2A - CO ₂ Entry through outside air in m ³ / h V _Fl - exhaust air volume flow in m ³ / h k _CO2F - CO ₂ concentration of the exhaust air in ppm AL = L <z - air exchange rate

With the relationships:

V _CO2A = 10 ^-6 . k _CO2A . V _Al , z = V _Al / V _R and k _CO2R = (V _CO2A + V _CO2P, n _P ). 10 ⁶ / (V _R z)

the CO ₂ concentration in the interior is calculated as follows:

k _CO2R = (V _CO2P 10 ⁶ n _P + k _CO2A V _Al ) / V _Al

Derived from this, the outside air volume flow is calculated:

V _Al = V _CO2P . 10 ⁶ . n _P / (k _CO2R - k _CO2A )

According to these equations, with the specifications:
k _CO2A - CO ₂ concentration in the outside air:
Empirical value about 450 ppm
V _CO2P - time-related CO ₂ charge per person; Values of this size depending on the degree of activity of a person are given in DIN 1946 Part 2;
k _{CO2R Max} - maximum permissible CO ₂ concentration in the room
the minimum outside air _{volume flow} V _{A / Min} for a given maximum CO ₂ content of the room air k _{CO2R Max} can be determined in two ways:

• 1st case: occupation of the vehicle n _P , z. B. by detecting the spring load known
  V _{Al Min} = V _CO2P . 10 ⁶ . n _P / (k _{CO2R Max} - k _CO2A ) (1.1)
• 2nd case: CO ₂ content of the room air known,
  Calculation of the occupation n _P from the measured CO ₂ concentration in the room air
  n _P = (k _CO2R - k _CO2A ). V _al . 10 ^-6 / V _CO2P
  V _{Al Min} = (k _CO2R - k _CO2A ). V _Al / (k _{CO2R Max} - k _CO2A ) (1.2)

Is the determined from occupation or gas concentration Minimum external air volume flow equal to zero, so it makes sense, anyway to specify a certain minimum external air volume flow to a possible accumulation of non-detectable gases and odors, which leads to so-called sick-building syndrome can lead to avoid.

Criterion 2

To compensate for the thermal load of the room is a certain Volume flow with a certain temperature required.

In the following, the relationships between supply air supply, their composition of external and circulating air and energy and power requirements are explained. Where:

• 1. E - energy supplied in kWh
• 2. P - supplied power in kW
• 3. V - volume flow in m ³ / h
• 4. T - temperature in ° C
• 5. c - specific heat in Wh / kg. K
• 6. m - mass in kg
• 7. φ - density in kg / m ³

with the indices:

• 1. _Al - outside air
• 2. _To - supply air
• 3. _mixed - mixed air
• 4. _Ul - recirculated room air (circulating air)
• 5. _R - space
• 6. _Fl - exhaust air
• 7. _Heating - heating mode
• 8. _Cooling - cooling mode
• 9. _Is - Actual

For the temperature of the room to be expended energy or power are calculated in principle according to the equations:

E _RZu = c. m _to . (T _R - T _To ) energy to be expended

P _RZu = c. φ. V _Zu . (T _R - T _Closed ) required power

The following technical boundary conditions must be considered:

• - Supply air temperature: For reasons of comfort and plant safety, the regulations set the limits T _ZuMin and T _ZuMax .
• - _Supply air volume flow: The minimum supply air volume flow V _ZuMin is determined by the air volume which must be enforced to ensure room air _circulation and by the minimum _external air volume flow V _AlMin required according to criterion 1.
  The maximum supply air delivery V _ZuMax is limited by the following factors:
  The supply air volume must be introduced so that discomfort caused by excessive flow velocities.
  The airways determine the flow resistance and thus the mechanical power required for the pumping. Ie. according to the volume flow certain cross sections are required.

For the plants to which the invention relates, the following assumptions apply:

• - V _Al = V _Fl , steady system
• - A representation of the air states in the h-x diagram causes the Presence of means for detecting the variables temperature and humidity. Vehicle air conditioners for temperate climates have in Generally no humidity control and thus no detection the outdoor and indoor air humidity. It is therefore assumed that in the most frequent operating cases of the relevant vehicle air conditioners Moisture content of the supply air only insignificantly from their composition from ambient and outdoor air is affected. That is why the energy requirement for the dehumidification of the supply air, as from the mixture of Volume flows independent value, attributable.
• - Approximation: T _Ul = T _Fl = mean T _R
• - variables that can not be influenced: T _Al , P _R variables: V _Al , T _Zu

The thermal load of the space P _R is determined by:

• - external weather conditions such as solar radiation intensity, Turbidity, temperature, humidity,
• - k-value of the vehicle,
• Movement state of the vehicle,
• - Occupation, this is in DIN 1946 Part 2, the assumed heat output ever Person, depending on their level of activity,
• - Heat emission of electrical consumers.

It causes a temperature change of the incoming supply air in the room by the amount ΔT _R = T _R - T _Zu

In case of control deviation (T _R ≠ T _Rsoll ), the actual room load can be determined according to the following equation:

P _R = c. φ. V _ZuIst . (T _RIst - T _ZuIst ) (2.1)

wherein a positive sign of (T _RIst - T _ZuIst ) or of P _R heat input into the room and thus a cooling demand and a negative sign corresponds to a heat extraction and thus heating demand.

In order to achieve the desired room temperature T _RSoll , the volumetric flow and the temperature of the supply air must be adjusted in such a way that it compensates the thermal load of the room, for which the following equations apply:

T _Zu = T _RSoll - ΔT _R (2.2)

P _R = c. φ. V _Zu . (T _RSOLL - T _To) (2.3)

T _Zu = T _RSoll - P _R / c. φ. V _To , where if T _Zu <T _{To Max} ,: T _To = T _{To Max} , and
if T _To <T _{To Min} ,: T _To = T _{To Min} . (2.3a)

V _Zu = P _R / ((T _RSoll - T _Zu ). C. Φ) with the condition V _{To Min} <= V _To <= V _{To Max} V _{Al Min} <= V _{To Min} (2.3b)

These relationships are shown graphically on an example of cooling and heating load in FIG. 2.

By mixing the volume flows of external and recirculated air, mixed air is created, with the temperature:

T _mixed = (V _Ul . T _Ul + V _Al . T _Al ) / (V _Ul + V _Al ) (2.4)

It can also be represented as a function of the ratio x _v = V _Al / V _Zu with V _Zu = V _Ul + V _Al :

T _mixed = x _v . (T _Al - T _Ul ) + T _Ul (2.4a)

From the equations:

P _Zu = V _Zu . c. φ. (T _mix - T _To) (2.5)

P _Zu = c. φ. (V _Al (T _Al - T _Ul ) + V _To (T _Ul - T _RSoll )) + P _R (2.5a)

or in representation as a function of the ratio x _v = V _Al / V _Zu

P _Zu = V _Zu . c. φ. (x _v . (T _Al - T _Ul ) + T _Ul - T _RSoll ) + P _R (2.5b)

It can be seen that the power requirement for the temperature control of the supply air proportional to the product of supply air volume flow and temperature difference between mixing and supply air is. Corresponds to the mixed air temperature of required supply air temperature so the energy requirement is zero, d. H. Ventilation mode.

In order to achieve the goal of the invention of equalizing T _R to T _desired with minimum energy input E, the following control of the outside air volume flow is required:

• Case 1: T _R <T _RSOLL (heating) ⇒ T _to must be greater than T _R
  T _Al <T _R ⇒ V _Al maximum
  T _Al <T _R ⇒ V _Al Minimum
• 2nd case: T _R <T _RSoll (cooling) ⇒ T _To be smaller than T _R
  T _Al <T _R ⇒ V _Al Minimum
  T _Al <T _R ⇒ V _Al maximum

In Fig. 3.1 the required thermal power is shown as a function of the mixing ratio outside / supply air volume flow at the same load and outside temperature for different operating cases.

Fig. 3.2 shows the required thermal performance as a function of outside temperature and room load at different mixing ratios outside / supply air volume flow.

Ventilation is understood to mean the reduction of the thermal load by the supply of non-treated outside air. For this applies:

P _Zu = 0 at T _Zu = T _Misch

T _F = T _Al + ΔT _R V _Al = V _F

In order to _adjust the room temperature to the setpoint (T _R = T _RSoll ), an outside air _{volume flow} is required, which is determined according to the following formula:

V _AlL = V _Zu = P _R / ((T _RSoll - T _Al ). C. Φ) (2.6)

From contexts set out above is as subject of the Invention the following method for controlling the air flow rates derived:

The supply air is expediently treated according to two criteria:

• 1. Indoor air quality: It is essentially determined by the occupation of the vehicle with persons and their degree of activity. As an indicator, the CO ₂ content of the room air can be considered.
• 2. Thermal load: It depends on the outer and inner Heat loads.

In order to minimize the use of energy while observing the marginal conditions, supply air delivery and mixture of the volume flows are determined according to the following rules:

• 1. The minimum external air content of the supply air is determined by the indoor air quality, regardless of the energy requirement. The number of persons in the room and their activities, and the resulting harmful gas content of the room air determine the minimum external air volume flow V _{Al Min} according to equation (1.1) or (1.2).
• 2. According to the room load, which consists of the actual values of Supply air volume flow and difference between room temperature and Supply air temperature according to equation (2.1) is determined are required supply air volume flow and the corresponding Supply air temperature according to equation (2.3a) and (2.3b) determined.
• 3. According to the direction and height of the temperature deviation of the outside air from the room air, the supply air volume and their fresh air proportion so determines that the difference between the mixing temperature according to Equation (2.4)) and the required supply air temperature after Equation (2.3a) is as small as possible. Here are the for the supply air already mentioned boundary conditions regarding temperature and To comply with flow rate.

The method can be implemented according to the program flowchart shown in FIG. 4, which forms part of the invention. The operating modes and the steps for setting them are explained below:

• 1. First, the minimum outside air _{volume flow} V _{AlMin is determined} according to the permissible CO ₂ concentration K _CO2RMAX .
• 2. According to equation (2.1), the room load P _R , which is the demand for cooling or heating power, is determined from the actual values of supply air volume flow and the difference between room temperature and supply air temperature.
• 3. If the outside air temperature T _Al is greater than or lower than the room air _temperature T _R for cooling _demand , the outside air _{volume flow} V _AlL required for ventilation operation is determined.
  • - If this is higher than the maximum possible delivery capacity, then the operating mode heating or cooling with maximum outside air _{volume flow} V _{AlMax is} set.
  • - it is less than the determined minimum in the first outdoor air volume flow V _LMIN, the mode is normal operation heating or cooling with minimal outdoor air volume flow V _almin set.
  • - If it lies between these limit values, the system operates in ventilation _mode with the outdoor air _{volume flow} V _AlL required for ventilation.
• 4. If the outside air can not reduce the room load due to its temperature, the control mode heating or cooling with the minimum outdoor air _flow V _{AlMin is set} to 1 _..
• 5. In all operating modes, the supply air _{volume flow} V _Zu is determined so that the value required for room air _circulation is reached, it contains the minimum _{external air volume flow} V _AlMin according to 1. and its temperature lies between the permissible limits T _ZuMin and T _ZuMax . If the required supply air volume flow V _{Zu is} greater than the determined outside air volume flow V _Al , this difference results in the recirculation air flow V _Ul .
• 6. In the modes of operation heating or cooling is the for controlling the supply air flow V _{To be} supplied as required by cooling or heating coil power P _Zu according to equation (2.5b) depending on the temperatures of the external and circulating air and their mixing ratio x _v as Default value calculated for the control of cooling unit or heating.

The following three examples show the energetic advantage of Invention clarifies:

It is the power requirement for the temperature of the interior in different operating cases according to the above-described simplified calculation method respectively

• a) for a system with constant air flow rates
• b) optimized for the same system with according to the invention Air flow rates determined.
• c) Control mode cooling
  assumed operating case: T _RIst = 26 ° C, T _ZuIst = 14.2 ° C, V _ZuIst = 2800 m ³ / h
  Room load: P _R = c. φ. V _ZuIst . (T _RIst - T _ZuIst ) = 0.28. 1.3. 2800. (26 - 14,2) = 12026,56 ≘ 12 kW (2.1)
  T _RSoll = 22 ° C
  T _Al = 18 ° C
  T _Ul = 24 ° C
  • a) Volume flows constant:
    V _to = 2800 m ³ / h
    V _Ul = 1400 m ³ / h

Required performance

P _to

= c. φ. (V _Al

, (T _Al

- T _Ul

) + V _To

, (T _Ul

- T _RSoll

)) + P _R

= 0.28. 1.3. (1400. (18 - 24) + 2800. (24 - 22)) + 1200 = 10980.8 ≘ 10.98 kW (2.5a)

• a) optimized flow rates
  Design of the plant:
  V _AlMax = 2800 m ³ / h
  T _ZuMin = 7 ° C

• - Occupation: 60 persons ⇒ V _Almin = 1200 m ³ / h
• - T _R <T _RSoll ⇒ _Cooling requirement
• - T _Al <T _R ⇒ Ventilation required outside air volume flow
  V _AlL = V _Zu = P _R / ((T _RSoll - T _Al ). C. Φ) = 12000 / ((22-18) .1, ^3, .28) = 8241.75 ≘ 8242 m ³ / h (2.6)
• - V _AlL <V _Almax ⇒ V _Al = V _AlMax = 2800 m ³ / h
  V _Ul = 0 m ³ / h, required supply air temperature
  T _Zu = T _RSoll - P _R / c. φ. V _Zu = 22 - 12000 / (1.3, 0.28, 2800) = 10.2 ° C ⇒ T _To <T _Min (2.3a)

Required performance

P _to

= c. φ. (V _Al

, (T _Al

- T _Ul

) + V _To

, (T _Ul

- T _RSoll

)) + P _R

= 0.28. 1.3. (2800. (18 - 24) + 2800. (24 - 22)) + 12000 = 7923,2 ≘ 7,92 kW (2.5a)

By reducing the proportion of recirculated air (to 0) and increasing the Outside air proportion (total supply air) is in the assumed operating case the power consumption by a factor of 1.3859 lower.

• 1st control operation heating
  assumed operating case:
  T _RIst = 20 ° C, T _ZuIst = 31.8 ° C, V _ZuIst = 2800 m ³ / h
  Room load: P _R = c. φ. V _ZuIst . (T _RIst - T _ZuIst ) = 0.28. 1.3. 2800. (20 - 31.8) = -12026.56 ≘ -12 kW (2.1)
  T _RSoll = 22 ° C
  T _Al = -7 ° C
  T _Ul = 20 ° C
  • a) Volume flows constant:
    V _Zu = 2800 m ³ / h
    V _Ul = 1400 m ³ / h

Required performance

P _to

= c. φ. (V _Al

, (T _Al

- T _Ul

) + V _To

, (T _Ul

- T _RSoll

)) + P _R

= 0.28. 1.3. (1400. (-7-20) + 2000. (20-22)) - 12000 = -27797.6 kW ≘ -27.80 kW (2.5a)

• a) optimized flow rates
  Design of the plant:
  V _AlMax = 2800 m ³ / h
  T _ZuMax = 60 ° C

• - Occupation: 20 persons ⇒ V _{AlMin '} = 400 m ³ / h
• - T _R <T _RSoll ⇒ Heating
• - T _Ul <T _R ⇒ V _Al = V _{Al Max} = 400 m ³ / h
• - T _Ul <T _RSoll ⇒ V _Zu = min., T _Zu = T _Zumax = 60 ° C
• - V _Zu = P _R / ((T _RSoll - T _Zumax ). C. Φ) - = 12000 / (( _22-60 ). 1.3. 0.28) = 868 m ³ / h (2.3b)
• - V _Ul = V _Zu - V _Almin = 468 m ³ / h

Required performance

P _to

= c. φ. (V _Al

, (T _Al

- T _Ul

) + V _To

, (T _Ul

- T _RSoll

)) + P _R

= 1.3. 0.28. (400 (-7-20) + 868 (20-22)) - 12000 = -16563 ≘ -16.56 kW (2.5a)

By reducing the supply air volume and reducing the proportion of outside air is in the assumed operating case, the power consumption by the factor 1.68 lower.

• 1. controlled ventilation operation
  assumed operating case:
  T _Rist = 23 ° C, T _ZuIst = 17.2 ° C, V _ZuIst = 2800 m ³ / h
  Room load: P _R = c. φ. V _ZuIst . (T _RIst - T _ZuIst ) = 0.28. 1.3. 2800. (23 - 17.2) = 5911 ≘ 6 kW (2.1)
  T _RSoll = 22 ° C
  T _Al = 15 ° C
  T _Ul = 24 ° C
  • a) Volume flows constant:
    V _Zu = 2800 m ³ / h
    V _Ul = 1400 m ³ / h

Required performance

P _to

= c. φ. (V _Al

, (T _Al

- T _Ul

) + V _To

, (T _Ul

- T _RSoll

)) + P _R

= 0.28. 1.3. (1400. (15 - 24) + 2800. (24 - 22)) + 6000 = 3452 ≘ 3.45 kW (2.5a)

• b) optimized flow rates
  Layout of the plant: V _Almax = 2800 m ³ / h
  • - Occupation: 30 persons ⇒ V _{AlMin '} = 600 m ³ / h
  • - T _RIst <T _RSoll ⇒ Cooling
  • - T _Al <T _R ⇒ Ventilation required outside air volume flow
  • - V _AlL = V _Zu = P _R / ((T _RSoll - T _Al ). C. Φ) - = 6000 / ((22 - 15). 1.3, 0.28) = 2354.8 m ³ / h (2.6)
  • - V _AlL <V _AlMin
  • - V _AlL <V _AlMax ⇒ V _Al = V _AlL = 2355 m ³ / h
    V _Ul = 0 m ³ / h

By reducing the proportion of recirculated air (to 0) and increasing the Outside air proportion (total supply air) is in the assumed operating case no cooling capacity required.

The power requirement as a function of the ratio external / supply air flow for these examples is shown in Fig. 3.1.

Claims (8)

1. A method for controlling fresh air and recirculated air volume flow in a ventilation system for the temperature of a room, in particular in a vehicle for passenger transport, wherein outside air and recirculation air flow form a supply air flow, in which

• a) a minimum _{external air volume flow} V _{AlMin is} determined, which must be supplied in order to comply with a limit value of the concentration of a noxious gas in the air of the room,
• b) the power requirement P _R required for the adaptation of the room air temperature T _R to a setpoint temperature T _Rsoll is determined on the basis of the actual values of the supply air _{volume flow} V _ZuIst and the difference between the room temperature T _RIst and the supply air temperature T _ZuIst ,
• c) the outside air _{volume flow} V _AlL required to obtain the setpoint temperature by supplying outside air is _determined on the basis of the power requirement P _R , the setpoint temperature T _Rsoll and the outside air temperature T _Al , and
• d) if the required power requirement is a heating demand and the outside air temperature T _{Al is} above the room air temperature, or
  if the required power requirement is a cooling requirement and the outside air temperature T _{Al is} below the room air temperature,
  • 1. If the required outside air _{volume flow} V _{AlL is} less than the maximum possible _delivery capacity and greater than the minimum external air _{volume flow} V _AlMin , this required outside air _{volume flow} V _{AlL is} supplied, and
  • 2. if the required outside air _{volume flow} V _{AlL is} smaller than the minimum outside air _{volume flow} , at least the minimum external air _volume flow is supplied.

2. The method according to claim 1, characterized in that when the required power requirement is a heating demand and the outside air temperature T _{Al is} above the room air temperature T _R ;

• 1. if the required outside air _{volume flow} V _{AlL is} greater than the maximum _delivery capacity of the system, the maximum possible outdoor air _{volume flow} V _AlL , V _{AlMax is} supplied and the supply air is heated.

3. The method according to claim 1, characterized in that when the required power requirement is a cooling demand and the outside air temperature T _{Al is} below the room air temperature,

• 1. If the required outside air _{volume flow} V _{AlL is} greater than the maximum _delivery capacity of the system, the maximum possible outdoor air _{volume flow} V _AlL , V _{AlMax is} guided and the supply air is cooled.

4. The method according to any one of the preceding claims, characterized in that the power requirement based on the formula
P _R = cφV _ZuIst (T _RIst - T _ZuIst )
where c is the specific heat and φ is the density of the supply air, V _is the supply air _{volume flow} , T _{R is} the room air temperature and T _is the supply air temperature. 5. The method according to any one of the preceding claims, characterized in that the required outside air _{volume flow} V _AlL according to the equation
V _AlL = P _R / ((T _RSoll - T _Al ) cφ)
where c is the specific heat and φ is the density of the supply air, T _{RSoll is} the target room air _temperature and T _{Al is} the outdoor air _temperature . 6. The method according to any one of the preceding claims, characterized in that the minimum _{external air volume flow} V _{AlMin is} determined based on the number of people in the room. 7. The method according to claim 6, characterized in that the room a Space of a passenger transport vehicle, and that the number of Persons determined by the spring load of the vehicle. 8. The method according to any one of claims 1 to 5, characterized in that the minimum _{external air volume flow} V _{AlMin is} determined based on the measured CO ₂ content of the room air.