DE102006009646B4 - Method and arrangement for simulating a room air flow - Google Patents

Abstract

method characterized for simulating a room air flow, that a reduced model space (6) of a space to be analyzed with filled with a compressed gas is set, the mean pressure and mean temperature so be that, with a suitable choice of the performance of the heating elements (9) and the volume flow at the gas inlet openings (7) of the flow state of the gas in model space by the same values of hydrodynamic similarity parameters Reynolds number, Rayleigh number and Prandtl number is characterized as in the room to be analyzed.

Description

The The invention relates to a method and an arrangement with which the Movement of air inside a building, a room or a passenger cabin on a smaller scale can be reproduced. The process according to the invention is described below referred to as high pressure modeling, the inventive arrangement is called high-pressure model in the following.

The Knowledge of spatial Distribution of air velocity, air temperature, humidity, pollutants, smells and pathogens is for the well-being and health of people in buildings and Transportation of great importance. In particular, it is in the planning of buildings, motor vehicles, rail vehicles and Passenger aircraft of interest, for a given interior, a given arrangement of heating elements, air inlets, air outlets and Wall materials as well as for a given number and distribution of persons the above sizes as To accurately predict the function of place and time.

at the prior art numerical Methods are the equations of fluid mechanics by means of a Computers solved and from the solutions the sought after sizes such as Example the flow velocity and the air temperature in the vicinity of persons. However, since room air flows are turbulent, their numerical simulation is characterized by great uncertainties. A reliable one Prediction of room air flows on the sole basis of numerical methods is therefore after the current state of the art not possible.

In Aerodynamics is the experimental method of wind tunnel modeling widespread. It is suitable for simulating forced convection, when an object such as an airplane of one flow of air caused by movement. According to the hydrodynamic similarity theory represents a scaled-down model of the aircraft in a wind tunnel then exactly to scale Replica of the real flow when the Reynolds number (Re) of original and model match.

at Room air currents This is in contrast to aerodynamic flow problems for mixed convection. This flow type is characterized in that it by both mechanical sources (Fan) as well as by thermal sources (heating elements) is caused and therefore, unlike forced convection, not just one, but by three similarity parameters is marked. This is the Reynolds number Re, around the Rayleigh number Ra and the Prandtl number Pr.

Want You have to simulate a room air flow in a model experiment according to the principles the hydrodynamic similarity theory Make sure the three similarity parameters Re, Ra and Pr have the same value as the model Original.

Out the literature (see, for example, the publication D. Mueller, I. Gores, R. Zielinski, Impact of the Thermal Load on the Room Airflow pattern; Roomvent 2004, 9th International Conference to Air Distribution in rooms; Sep 5-8, 2004, Portugal) are experimental methods for the investigation of room air flows in which the space to be analyzed is constructed on the original scale becomes. Here are the similarity parameters automatically equal to original and model, however, this procedure is associated with a high construction cost and therefore for many Not cases practical. From the publication "The fluid mechanics of natural ventilation" by P.F. Linden, Annual Review of Fluid Mechanics, 1999, vol. 31, 201-238 is further an experimental method known in which to be analyzed Space on a reduced scale built and used as a model substance water instead of air. By a suitable choice of heating power and flow rate can at this method the match be reached by Re and Ra. The parameter Pr of water is however, by more than an order of magnitude above that of air. Thus, the water flow in the model is not with the airflow identical in the original. Also when using air under normal pressure it is impossible, in a scaled-down model, the concurrence of Re, Ra, and To assure Pr because the for this required temperature differences with the cube of the model scale increase. So would have to for example in the case of a model scale from 1:10 the temperature difference between heating element and air inlet Calculated from 10K purely computationally to 1000K, which is not practical is.

In the pamphlets "Steady State Natural Convection in Empty and Partitioned Enclosures at High Rayleigh Numbers "(D.A. Olson, L.R. Glicksman, H.M. Ferm, Trans. ASME, vol. 112, 1990 pp. 640-647) and "Design of an Experimental Facility for Building Airflow and Heat Transfer Measurements "(Dissertationsschrift Mohammad Elyyan, Oklahoma State University, 2005) are gases with high density such as the refrigerant 114 on their suitability as working substance for Model experiments tested. However, the experiments described are only included Normal pressure performed. This is at most a scale factor reachable from 1: 5.

The present invention is thus the It is the object of the invention to provide a method and an arrangement which make it possible to simulate a room air flow in a strongly reduced model, characterized by scale factors of at least 1:10, while retaining all three fluid-mechanical similarity parameters Re, Ra and Pr.

The These objects are achieved according to the invention by the features of the independent claims 1 and 5 solved, while the dependent claims advantageous developments of the invention can be seen.

When solution for the The tasks set above serve the purpose of high-pressure modeling. This method is characterized in that the reduced Model of the space to be examined in a pressure vessel with filled with a compressed gas whose mean pressure and average temperature are controllable. Since the kinematic viscosity and thermal diffusivity compressed gases such as air or sulfur hexafluoride can depend heavily on pressure and temperature, can by suitable Choice of these two sizes as well the heating power and volume flows a match of all achieved three hydrodynamic similarity parameters become.

Further details and advantages of the invention will become apparent from the following, with reference to 1 illustrated embodiment.

To 1 the high-pressure model according to the invention comprises a pressure vessel ( 1 ) with safety valve ( 2 ), which contains a compressed gas as the working medium. Before the start of the investigations, the pressure vessel is closed by means of a vacuum pump ( 3 ) evacuated. Subsequently, in a gas supply unit ( 4 ) stored working fluid pumped into the pressure vessel. In the pressure vessel is the replicated on a reduced scale model space ( 6 ), which is the subject of the flow investigation in the following.

The model room is equipped with heating elements ( 9 ) whose heating power is to be dimensioned in a manner familiar to the person skilled in the art so that the similarity parameter Ra agrees with the original. The model space also has one or more gas inlet openings ( 7 ) and one or more gas outlet openings ( 8th ). The mass flows at the gas inlet openings are to be dimensioned in a manner familiar to the person skilled in the art so that the similarity parameter Re matches the original. The temperature of the working medium at the gas inlet openings ( 7 ) by means of a to a cooling circuit ( 11 ) with a coolant pump ( 12 ) connected heat exchanger ( 10 ) kept constant.

Inside the model room are one or more person models ( 19 ), with which on the one hand the heating effect and the respiration of persons can be modeled and on the other hand, physical quantities can be measured, which are important for the thermal comfort of people.

The flow generated inside the model space is controlled by local sensors ( 13 ) such as thermocouples and measured in a first evaluation unit ( 14 ) analyzed. It is also within the scope of the invention, the flow conditions with non-contact optical flow measuring devices ( 16 ), such as a laser Doppler anemometer or a particle image velocimetry system, and with the aid of a second evaluation unit ( 17 ) or the temperature distribution in the model space with a thermography system installed inside or outside the pressure vessel ( 18 ) to investigate.

1

pressure vessel

2

safety valve

3

vacuum pump

4

Gas supply unit

5

window

6

model space

7

Gas inlet opening

8th

Gas outlet

9

heating element

10

heat exchangers

11

Cooling circuit

12

Coolant pump

13

sensor

14

first evaluation

15

power supply

16

optical flow meter

17

second evaluation

18

Termografiesystem

19

people model

20

suspended to visualize the flow (Tracer)

Claims (10)

Method for simulating a room air flow, characterized in that a reduced model space ( 6 ) of a space to be analyzed is filled with a compressed gas whose average pressure and mean temperature are adjusted so that, with a suitable choice of the power of the heating elements ( 9 ) and the volume flow at the gas inlet openings ( 7 ) the flow state of the gas in the model space is characterized by the same values of the hydrodynamic similarity parameters Reynoldszahl, Rayleighzahl and Prandtlzahl as in the space to be analyzed. A method according to claim 1, characterized in that the thermal comfort by measuring at least one in the model space ( 6 ) person model ( 19 ) is determined. Method according to one of claims 1 or 2, characterized in that the distribution of flow velocity, temperature, pressure, heat radiation and concentration of gases by sensors ( 13 ) and / or optical flowmeters ( 16 ) at several positions in the model space ( 6 ) is detected. Method according to one of claims 1 to 3, characterized that the spatial Distribution of flow velocity, Temperature or particle concentration, directly or indirectly is visualized. Arrangement for simulating a room air flow, characterized in that it consists of a pressure vessel filled with compressed gas ( 1 ), a model space ( 6 ), a gas supply unit ( 4 ) with a vacuum pump ( 3 ), a cooling circuit ( 11 ) with a coolant pump ( 12 ) and a heat exchanger ( 10 ), Flowmeters ( 16 ) and Termografiesystemen ( 18 ) and from evaluation ( 14 . 17 ) and power supply units ( 15 ), where the model space ( 6 ) at least one gas inlet and outlet ( 7 . 8th ) and in its interior at least one heating element ( 9 ) and at least one person model ( 19 ) and that it is designed to carry out a method according to any one of claims 1 to 4. Arrangement according to claim 5, characterized in that the walls of the pressure vessel ( 1 ) and the model space ( 6 ) are made partially or completely of an optically transparent material, wherein the walls of the model space ( 6 ) can be heated or cooled with a given temperature surface. Arrangement according to one of claims 5 or 6, characterized in that at different positions in the interior of the model space sensors ( 13 ), with which the average temperature, the flow rate, the average pressure, the density, the humidity or the concentration of chemical substances contained in the compressed gas can be measured. Arrangement according to one of claims 5 to 7, characterized in that the flow velocity by means of a installed in the interior or outside of the pressure vessel flow meter ( 16 ) and with an evaluation unit ( 17 ) can be visualized. Arrangement according to one of claims 5 to 8, characterized in that the temperature distribution by means of an installed inside or outside of the pressure vessel Termografiesystems ( 18 ) can be measured. Arrangement according to one of claims 5 to 9, characterized in that the at least one person model ( 19 ) is heatable and having an actuator system for movement, a respiratory system and a plurality of temperature, heat flow, radiation and speed sensors.