Dual-Flow Desiccant Air Handling for Humidified Heating
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Solution Overview
Problem
Existing desiccant air handling units are energy-intensive and ineffective in heating mode for providing hot air with high humidification, and they concentrate pollutants by reinjecting stale air, which poses risks of freezing and inefficient humidity regulation.
Innovation Solution
A dual-flow air handling unit with a desiccant wheel, recovery heat exchanger, regeneration heating coil, enthalpy heat exchanger, and supply air humidifier, where the enthalpy heat exchanger downstream of the desiccant wheel recovers humidity from stale air to reduce the need for additional humidification and prevent pollutant reinjection, and the enthalpy heat exchanger's placement upstream of the regeneration heating coil prevents freezing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heat pump and cooling system are used to dehumidify air, then humidity control is achieved, but energy consumption increases significantly
Solution Approach 1:
The patent changes the fundamental parameter from active cooling-based dehumidification to desiccant-based dehumidification. The desiccant wheel uses hygroscopic materials to absorb moisture from air through adsorption, eliminating the need for energy-intensive heat pump compression and cooling cycles while maintaining effective humidity control.
Solution Approach 2:
The patent replaces the mechanical heat pump system with a desiccant wheel system that uses chemical adsorption rather than mechanical compression and phase change. This substitution eliminates the need for refrigerants, compressors, and condensing coils, significantly reducing energy consumption while achieving the same dehumidification function.
2Use of energy by moving object
If stale air is reinjected mixed with fresh air, then energy efficiency improves through heat recovery, but pollutant concentration increases
Solution Approach 1:
The patent segments the air handling into separate fresh air and stale air paths. Fresh air is drawn in and conditioned independently through the desiccant wheel and heating coil, while stale air is separately exhausted. This segmentation prevents pollutant reinjection while still allowing heat recovery between the two air streams through the heat exchanger.
Solution Approach 2:
The patent extracts the harmful function of pollutant reinjection by completely separating the fresh air supply path from the stale air exhaust path. The heat exchanger extracts only the thermal energy from stale air without allowing the air streams to mix, thus recovering energy while eliminating pollutant concentration in the fresh air supply.
3Use of energy by moving object
If a desiccant wheel is used for dehumidification, then energy consumption is reduced, but heating mode efficiency decreases in cold seasons
Solution Approach 1:
The patent merges the desiccant wheel system with a heating coil system to create a hybrid air handling unit. The desiccant wheel handles dehumidification while the heating coil provides supplemental heating capability. This combination allows the system to maintain low energy consumption during dehumidification while achieving reliable heating performance in cold seasons by activating the heating coil when needed.
Solution Approach 2:
The patent creates a multi-functional air handling unit that can operate in both dehumidification mode and heating mode. The desiccant wheel provides dehumidification function, while the heating coil adds heating function, making the system universal enough to handle various seasonal conditions effectively without sacrificing energy efficiency.
4Reliability
If fresh air is drawn from outside in cold conditions, then air renewal is achieved, but freezing risk increases
Solution Approach 1:
The patent applies preliminary heating action to fresh air before it enters the desiccant wheel and other downstream components. The heating coil is positioned to preheat the incoming fresh air, raising its temperature above freezing point even when outside air temperatures are below zero. This preliminary action prevents freezing of water in the humidifier and other components while maintaining effective air renewal.
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
The dual-flow air handling unit efficiently provides hot air with constant humidification between 10 and 20 g/kg while reducing energy consumption, minimizing pollutant concentration, and preventing freezing of components, thus addressing the limitations of existing systems.
Implementation Method 1
a heat recovery exchanger interposed on the two air circulation paths and providing heat exchange between the stale air drawn from the zone and the fresh air drawn from the outside
Implementation Method 2
an enthalpy heat exchanger interposed on the two air circulation paths between the desiccant wheel and the regeneration heating coil, so that the regeneration heating coil and the recovery heat exchanger are upstream of the enthalpy heat exchanger on the return path, this enthalpy heat exchanger providing a heat and moisture exchange between the stale air taken from the zone and the fresh air blown into the zone
Implementation Method 3
a desiccant wheel interposed on the two air circulation paths
Implementation Method 4
a regeneration heating coil placed on the return path upstream of the desiccant wheel and downstream of the heat recovery exchanger, and providing heating of the stale air for regeneration of the desiccant wheel
Implementation Method 5
a supply humidifier placed on the supply air path downstream of the heat recovery exchanger
Data Source
Figure 1
AI summary
The invention relates to a dual-flow desiccant air handling unit (1) comprising, interposed on a return air duct (20R) and a supply air duct (20S) between the outside (EXT) and the area (ZO) to be treated, a desiccant wheel (21), a heat recovery exchanger (22), and an enthalpy heat exchanger (26) placed between the desiccant wheel and the heat recovery exchanger, providing heat and humidity exchange between the stale air drawn from the area and the fresh air supplied to the area. This unit also includes a regeneration heating coil (24R) and optionally a return air humidifier (25R) placed on the return air duct, as well as a heating coil (24S) and a supply air humidifier (25S) placed on the supply air duct. The present invention finds application in the field of air treatment for an aquatic facility.