Patient Support Surface Air Conditioning for Enhanced Evaporation
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Solution Overview
Problem
Existing microclimate management (MCM) capable support surfaces in hospital beds are limited by the properties of unconditioned ambient air, restricting their ability to achieve enhanced evaporative performance and heat transfer.
Innovation Solution
A method involving chilling unconditioned ambient air to achieve 100% relative humidity, demoisturizing it, and optionally heating the chilled air before supplying it to the support surface to enhance dry and wet flux capacities, thereby increasing total heat withdrawal capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unconditioned ambient air is used for microclimate management, then the system is simple and easy to operate, but the evaporative performance and heat transfer capability are limited
Solution Approach 1:
The patent applies parameter changes by conditioning the air (changing temperature and humidity parameters) to achieve desired evaporative performance. The air is chilled to remove moisture and then heated to achieve the target temperature while maintaining low humidity, thereby enhancing evaporative cooling capability beyond what unconditioned ambient air can provide.
Solution Approach 2:
The patent uses preliminary action by pre-conditioning the air (chilling and demoisturizing) before it reaches the support surface. This preliminary treatment removes moisture from the air through chilling to the dew point, and then the pre-cooled, dry air is heated to the desired temperature, ensuring optimal evaporative performance is achieved before the air contacts the patient.
2Reliability
If air is chilled to achieve 100% relative humidity for demoisturizing, then evaporative cooling performance is enhanced, but energy consumption increases
Solution Approach 1:
The patent exploits phase transitions by chilling the air to its dew point where water vapor condenses into liquid form. This phase change from vapor to liquid efficiently removes moisture from the air. The condensed moisture is then removed from the system, and the chilled, dry air is reheated to the desired temperature, achieving low humidity conditions that enhance evaporative cooling.
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 method significantly enhances evaporative cooling and heat transfer performance beyond what is achievable with unconditioned ambient air, improving skin comfort and reducing pressure ulcer risk by increasing total heat withdrawal capacity.
Implementation Method 1
chilling the unconditioned ambient air to a temperature at least as low as that required to achieve 100% relative humidity, thereby demoisturizing the air
Implementation Method 2
heat transfer from the occupant's skin can cause molecules of perspiration present at the interface between the support surface and the occupant's skin to acquire enough energy to break free, i.e. evaporate
Implementation Method 3
a stream of air flows through the interior of the support surface. Provided the air is cooler than the occupant's skin, the internal airstream acts as a heat sink
Data Source
AI summary
A method for controlling performance of an MCM capable support surface having a flowpath for guiding a stream of air along at least a portion of the surface, comprises specifying a desired evaporative rate greater than an evaporative rate achievable with unconditioned ambient air, chilling the unconditioned ambient air to a temperature at least as low as that required to achieve 100% relative humidity, thereby demoisturizing the air, and supplying the chilled, demoisturized air to the flowpath. The method may also include the step of heating the chilled, demoisturized air prior to step of supplying it to the flowpath. A system for carrying out the method includes a microclimate management (MCM) capable support surface 22, a chiller 60 for cooling air to be delivered to the MCM capable surface, a user interface 42 for receiving instructions concerning desired microclimate management performance, and a controller 50, responsive to the instructions, for operating the chiller.