Passenger Compartment Humidity Tracing for Fresh Air Flow Measurement
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Solution Overview
Problem
Current methods for measuring fresh air volume flow in vehicles, particularly rail vehicles, are complex and pose safety risks due to the use of carbon dioxide as a tracer gas, requiring extensive equipment and safety measures.
Innovation Solution
The method involves using water vapor as a tracer gas, introducing a defined water vapor mass flow into the passenger compartment, monitoring air humidity, and calculating the fresh air volume flow using a specific equation, which eliminates the need for hazardous safety measures associated with carbon dioxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carbon dioxide is used as a tracer gas for measuring fresh air volume flow, then measurement precision is improved, but safety risks and device complexity increase significantly
Solution Approach 1:
The patent replaces expensive and hazardous carbon dioxide tracer gas with inexpensive water vapor that can be easily generated and safely dispersed. Water vapor is introduced through evaporation from a reservoir, providing a safe, cost-effective alternative that eliminates the need for specialized safety equipment while maintaining measurement capability through humidity sensing.
Solution Approach 2:
The patent changes the physical parameter used for tracer gas from carbon dioxide concentration measurement to water vapor concentration measurement. By monitoring humidity levels instead of gas concentration, the system achieves the same measurement objective (fresh air volume flow) while eliminating safety hazards associated with carbon dioxide accumulation.
2Measurement precision
If carbon dioxide tracer gas measurement system is implemented, then fresh air volume flow can be determined, but device complexity and cost increase due to required safety equipment
Solution Approach 1:
The system replaces complex carbon dioxide delivery and monitoring equipment with simple water vapor generation using basic evaporation from a reservoir. The tracer substance (water vapor) is inexpensive, easily generated, and safely disperses without requiring specialized storage, handling, or detection equipment beyond standard humidity sensors.
Solution Approach 2:
The patent replaces the mechanical gas delivery system (cylinders, regulators, mass flow controllers) with a passive evaporation system. Water vapor is introduced through natural or assisted evaporation from a liquid reservoir, eliminating complex mechanical components while maintaining controlled introduction of the tracer substance for measurement purposes.
3Object-affected harmful factors
If water vapor is used as tracer gas instead of carbon dioxide, then safety risks are eliminated, but measurement personnel's water output must be accounted for
Solution Approach 1:
The system incorporates feedback by continuously monitoring humidity levels and using this information to calculate and compensate for water vapor sources. By measuring the actual humidity change over time and knowing the water vapor introduction rate, the system can subtract the contribution from measurement personnel's respiration and perspiration to determine the accurate fresh air volume flow.
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
This approach simplifies the measurement process, reduces safety risks, and provides a precise calculation of fresh air volume flow without the dangers posed by carbon dioxide, using readily available and inexpensive water vapor.
Implementation Method 1
Introducing or generating a defined mass flow of water vapor into a passenger compartment of the vehicle
Implementation Method 2
Monitoring the humidity in the passenger compartment of the vehicle
Data Source
AI summary
The invention relates to a method for determining a fresh air volume flow in a vehicle for transporting people, comprising the steps of: a) introducing or generating a defined water vapour mass flow into/in a passenger compartment (1) of the vehicle; b) monitoring the air humidity in the passenger compartment of the vehicle; and c) once a quasi-stationary air humidity has been reached in the passenger compartment (1), calculating the fresh air volume flow on the basis of the following equation (formula 1), where (aa) is fresh air volume flow [m³/h]; (bb) is mass of the evaporated water in the compartment [kg/h]; (cc) is number of people in the space; (dd) is water mass flow produced by one person; (ee) is density of the fresh air (moist air) [kg/m³]; (ff) is specific air humidity of the fresh air [kg/kg]; (gg) is density of the ambient air (moist air) [kg/m³]; and (hh) is specific air humidity of the ambient air [kg/kg]. The invention also relates to a device for carrying out such a method.