Ventilation and air conditioning system with a passive emergency cooling mode
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Solution Overview
Problem
Modern ventilation and air conditioning systems in nuclear power plants face a short grace period of approximately 2 hours before equipment reaches maximum temperature in case of a power outage, necessitating an emergency cooling solution that is easy to install and maintain.
Innovation Solution
A ventilation and air conditioning system that switches passively from active cooling to natural convection cooling using heat storage elements, specifically phase change materials (PCMs), and a non-return damper, allowing for continued cooling even without electrical power, with automatic reversion to normal cooling when power is restored.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If active cooling system is used, then cooling efficiency is improved, but system complexity and power consumption increase
Solution Approach 1:
The cooling system is segmented into two independent subsystems: an active cooling subsystem (ventilation duct with fan) and a passive cooling subsystem (heat storage elements). This segmentation allows the system to switch between modes and reduces the complexity burden by separating the high-performance active component from the simple passive component.
Solution Approach 2:
The passive cooling subsystem is designed to be self-service, using heat storage elements that automatically absorb or release heat based on temperature conditions without requiring external control or power input. The non-return damper also operates passively, opening or closing based on airflow direction alone.
2Reliability
If active cooling system is used, then cooling reliability is improved, but power consumption increases
Solution Approach 1:
The heat storage elements are pre-charged during nighttime or low-load periods when power consumption is less critical, storing thermal energy that will be used during peak demand or power outage periods. This preliminary action ensures cooling reliability is maintained without continuous high power consumption.
Solution Approach 2:
The system operates in periodic cycles, switching between active cooling mode (when power is available) and passive cooling mode (when power is unavailable or during peak periods). This periodic operation reduces overall power consumption while maintaining cooling reliability through the complementary passive subsystem.
3Use of energy by moving object
If passive cooling mode is activated, then power consumption is reduced, but cooling capacity decreases
Solution Approach 1:
The system changes operational parameters by switching between forced convection (active mode with fan) and natural convection (passive mode without fan). This parameter change allows the system to adapt cooling capacity to match demand, using lower-power natural convection when full cooling capacity is not required.
Solution Approach 2:
The cooling system uses a composite approach combining active mechanical cooling components with passive thermal storage materials. The heat storage elements act as a thermal buffer, providing supplemental cooling capacity during passive mode operation, effectively creating a hybrid system that maintains adequate cooling with reduced power consumption.
4Extent of automation
If non-return damper is added, then automatic mode switching is improved, but device complexity increases
Solution Approach 1:
The control function is achieved by replacing complex electronic control systems with a simple mechanical non-return damper that responds automatically to airflow direction. The damper uses the kinetic energy of the airflow itself to open or close, eliminating the need for sensors, actuators, or control electronics while achieving automatic mode switching.
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
Extends the grace period to 24 hours, ensuring safe equipment operation and reducing costs by maintaining acceptable room temperatures without additional electrical equipment, thus enhancing safety and lowering the classification of active cooling system components.
Implementation Method 1
A phase change material (PCM) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy
Implementation Method 2
Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, PCMs are classified as latent heat storage units
Implementation Method 3
In normal operation the supply air is led through a housing which contains PCM modules (preferably installed in an earthquake proven construction). The supply air with a temperature of approx. +17 °C freezes the PCM inside the modules
Implementation Method 4
This differential pressure of air via the block of PCM modules ensures, that a special non-return damper, preferably with weight lever is kept closed, so that the air must pass the PCM modules... Once the closing force falls below the opening force, the damper opens
Implementation Method 5
The air inside the room is heated by the electrical (or other heat-dissipating) installations and rises to the room ceiling. The warmer the room air temperature under the ceiling rises, the higher the density difference of air outside and inside the PCM block is
Implementation Method 6
The air flows through the gaps between the vertically installed PCM modules and cools down when passing the surface of the PCM plates. The heat of the air passes into the PCM material which has a noticeable peak at a certain temperature range
Implementation Method 7
The constant temperature of the PCM in a wide range of the melting capacity is the main positive effect of latent energy storage and beneficial for the room air temperature behavior
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An objective of the present invention is to provide some kind of emergency cooling for an active ventilation and air conditioning system (6) in the event of loss of active cooling functions, in particular due to power outage. According to the invention this aim is reached by a ventilation and air conditioning system (6) for a room (2), the room (2) containing a heat source and the ventilation and air conditioning system (6) comprising a cooled air supply (12) and a ventilation duct (10), the ventilation duct (10) comprising a primary inlet (24) being connected to the cooled air supply (12) and an outlet (14) leading into the room (2), wherein a number of heat storage elements (30) is arranged inside the ventilation duct (10) between the primary inlet (24) and the outlet (14), such that during operation of the cooled air supply (12) there is a forced stream of cooled air through the ventilation duct (10), thereby cooling and preferably freezing the heat storage elements (30), wherein there is a secondary inlet (36) into the ventilation duct (10) which is in flow communication with the room (2) and which during operation of the cooled air supply (12) is closed by a damper (40), and wherein the damper (40) is designed to automatically open in a passive manner when the forced stream of cooled air from the cooled air supply (12) stops, such that a natural convection airflow through the ventilation duct (10) is supported, wherein the natural convection airflow is cooled by transferring heat to the heat storage elements (30).