Air Handling Unit Defrost Heating With Thermal Energy Storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In air treatment systems with heat recovery via heat pumps, the defrosting of DX-coils using reversible operation leads to a significant temperature drop in the supply air stream, which is costly and inefficiently addressed by high-power electrical or water heating systems.
Innovation Solution
An accumulator medium is used to store heat energy during non-defrosting operations, which is then utilized during defrosting to maintain supply air temperature through a heating coil and circulation system, eliminating or reducing the temperature drop without the need for high-power electrical heating or external heating systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reversible operation is used to defrost the evaporator, then the evaporator is defrosted effectively, but the supply air temperature drops significantly
Solution Approach 1:
The system accumulates thermal energy in an accumulator medium (water or brine) in the accumulator tank during non-defrosting operation. This preliminary storage of heat energy enables the system to compensate for temperature drops during subsequent defrosting operations without affecting supply air temperature.
Solution Approach 2:
An accumulator medium (water or brine) serves as an intermediary thermal energy storage medium between the heat pump system and the supply air. The accumulator medium absorbs excess heat during normal operation and releases it during defrosting, mediating the thermal balance to prevent supply air temperature drops.
2Temperature
If high-power electrical heating or water heating batteries are installed to maintain supply air temperature during defrosting, then the temperature drop is prevented, but the installation and operating costs increase significantly
Solution Approach 1:
The system uses itself to solve the temperature drop problem during defrosting. The heat pump accumulates thermal energy in the accumulator medium during normal operation, and this stored energy is then used to compensate for supply air temperature drops during defrosting, making the system self-sufficient without external high-power heating assistance.
Solution Approach 2:
The system recovers and stores thermal energy that would otherwise be wasted during non-defrosting operation. This recovered thermal energy is stored in the accumulator medium and later utilized during defrosting operations, eliminating the need for additional high-power heating systems.
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 solution provides a cost-effective and efficient method to maintain supply air temperature during defrosting, utilizing stored heat energy and waste heat from the heat pump and control cabinet to reduce operational costs and eliminate the need for high-power heating systems.
Implementation Method 1
accumulate heat energy in an accumulator medium during non-defrosting operation
Implementation Method 2
heat exchange between the accumulator medium and supply air flow
Implementation Method 3
recover heat from the extract air through a first so-called DX-coil (direct expansion coil), which in heating operation acts as a evaporator, and transfers this heat to the supply air through a second DX-coil, which in heating operation acts as a condenser
Implementation Method 4
a first so-called DX-coil (direct expansion coil), which in heating operation acts as a evaporator
Implementation Method 5
the refrigerant in the heat pump refrigerant circuit is sent in the opposite direction, i.e. the heat is temporarily collected from the supply air and sent to the extract air to defrost the first DX-coil
Implementation Method 6
a second DX-coil, which in heating operation acts as a condenser
Data Source
AI summary
Method and device for reducing or eliminating a temperature drop of the supply air temperature during defrost operation, at an air handling unit (1) which is arranged with a heat pump (2) for recovering heat from an extract air stream (3) and transfer to a supply air stream (4). During defrosting of a first DX-coil (5), arranged in the extract air stream (3), by reversible operation of the heat pump (2), accumulated heat energy (E) is used for reduction or elimination of the temperature drop in the supply air temperature during the defrost operation, and which energy has been stored in an accumulator medium (7) which is at least partially in contact with the supply air flow (4). The stored energy (E) is delivered by heat exchange with the supply air stream (4) in a position after a second DX-coil (6) through a heating coil (8) arranged in the supply air stream (4).