Method and device for determining the air change rate of a room or building
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Solution Overview
Problem
Current methods for determining the air renewal rate of a room are either costly, time-consuming, or unsuitable for various building types, as they often require complex setups or cannot account for external conditions effectively.
Innovation Solution
A method involving controlled gas flow rates and concentration measurements using a diffusive model to calculate the air renewal rate over a short period, allowing for in situ determination with reasonable precision and moderate cost, using gases like H2O, CO2, or SF6, and employing models such as R-C or ARX to analyze gas concentration variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the blower door test method is used to determine air exchange rate, then the measurement can be performed with simple equipment, but the results require complex physical models for extrapolation and do not adequately capture external conditions
Solution Approach 1:
The patent changes the measurement parameters by using small pressure differences (close to natural conditions) instead of large pressure differences, and by measuring multiple parameters (pressure difference, temperature, humidity, wind speed, wind direction) simultaneously to capture external conditions, thereby achieving accurate air exchange rate measurement without complex extrapolation models
Solution Approach 2:
The patent introduces an intermediary measurement approach by using a partial envelope (such as a room or zone) rather than the entire building, which simplifies the measurement setup while still providing representative data through the use of computational models that account for the relationship between the partial envelope and the whole building
2Measurement precision
If the tracer gas method is used to determine air exchange rate, then the measurement accounts for natural measurement conditions, but the method is costly and requires long measurement times
Solution Approach 1:
The patent extracts the essential measurement function from the complex tracer gas method by using a simplified approach that measures pressure difference, temperature, humidity, and wind conditions without requiring actual tracer gas injection, thereby achieving accurate air exchange rate determination in a fraction of the time
Solution Approach 2:
The patent replaces expensive and time-consuming tracer gas with inexpensive, readily available environmental parameters (pressure, temperature, humidity, wind data) that can be measured quickly using standard sensors, achieving the same measurement objective at lower cost and with much shorter measurement duration
3Productivity
If the blower door test uses large pressure differences, then the airflow rates can be measured directly, but the results do not reflect the effect of external conditions on the building
Solution Approach 1:
The patent applies dynamics by measuring air exchange rate under varying natural conditions (different pressure differences, temperatures, wind speeds, and wind directions) rather than static controlled conditions, allowing the measurement to adapt to and capture the real-world behavior of the building envelope
Solution Approach 2:
The patent creates a multi-functional measurement system that simultaneously measures pressure difference, temperature, humidity, wind speed, and wind direction, allowing a single measurement campaign to provide comprehensive data about building performance under various external conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid, precise, and cost-effective determination of air renewal rates in various premises, minimizing the influence of external conditions and internal absorption phenomena, suitable for all types of buildings.
Implementation Method 1
a diffusive model expressing a temporal variation of a concentration of the given gas inside the room depending on a concentration of the given gas outside the room and physical parameters of the room from which the value of the air renewal rate is calculable
Data Source
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AI summary
The invention relates to a method for determining the air change rate (ACH) of a room or building, comprising steps in which: a measurement programme is carried out over at least two successive time periods D k corresponding to different flow rates of a given gas q k applied in the room or building, which measurements can be used to determine the concentration of the gas inside the room or building c ik at shorter time intervals, as well as to determine the concentration of the gas outside the room or building c ek at shorter time intervals; the value of the air rate change (ACH) of the room or building is determined by merging (i) a diffusive model expressing the time-based variation in the concentration of the gas inside the room or building c ik as a function of the concentration of the gas outside the room or building c ek and physical room or building parameters from which the air change rate (ACH) of the room or building can be calculated, and (ii) the measured change c ik (t) in the concentration of the gas inside the room or building c ik as a function of time.