Wastewater Tank Heat Pump Control Using Partial Freezing
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Solution Overview
Problem
Current cleaning devices, such as washing machines and dishwashers, face inefficiencies in heat recovery from waste water, as they do not effectively utilize the latent heat from phase transitions, leading to suboptimal energy reuse.
Innovation Solution
The controller manages the heat pump to extract heat from the waste water tank until part of the process water freezes, leveraging latent heat, and then melts the ice using heated water from the tub to maximize heat transfer and energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If heat is extracted from waste water tank using conventional heat pump method, then heat is transferred to process water, but the amount of heat extracted is limited and energy efficiency is suboptimal
Solution Approach 1:
The patent utilizes the phase transition of water from liquid to solid (freezing) to extract latent heat from the waste water tank. By allowing part of the process water in the waste water tank to freeze, the system captures the latent heat of fusion, significantly increasing the amount of heat extracted compared to conventional heat pump methods that only utilize sensible heat. This resolves the contradiction by transforming the limiting factor from sensible heat capacity to latent heat capacity.
2Loss of energy
If heat pump operates to freeze part of process water in waste water tank, then latent heat is utilized for larger heat extraction, but the system complexity increases due to phase transition control
Solution Approach 1:
The system uses the waste water tank's own contents (process water) as the freezing medium to extract heat. The process water in the tank serves dual purposes: as the medium to be heated later and as the freezing medium for heat extraction. This self-service approach eliminates the need for separate freezing agents or complex external systems, reducing overall system complexity while achieving high heat recovery efficiency through latent heat utilization.
3Loss of energy
If ice is formed in waste water tank to maximize heat extraction, then latent heat is fully utilized, but the tank may become completely frozen blocking further heat transfer
Solution Approach 1:
The patent deliberately allows only partial freezing of the process water in the waste water tank rather than complete freezing. This partial action approach ensures that while sufficient latent heat is extracted to maximize heat recovery efficiency, enough liquid water remains to maintain thermal contact and heat transfer pathways. The partial freezing state balances heat extraction efficiency with system reliability, preventing complete freezing that would block further heat transfer.
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 energy efficiency by extracting a larger amount of heat from the waste water tank, allowing for more effective reuse and reduced energy consumption.
Implementation Method 1
to extract heat from the waste water tank with the heat pump for so long that part of the process water in the waste water tank freezes. This makes it possible, thanks to the use of the latent heat from the phase transition, to extract a significantly larger amount of heat from the waste water tank.
Implementation Method 2
part of the process water in the waste water tank freezes. This makes it possible, thanks to the use of the latent heat from the phase transition
Implementation Method 3
a heat pump to extract heat from the waste water tank and feed it to the process water in the tub
Implementation Method 4
at least part of the ice in the waste water tank is melted again by water being conducted from the vat into the waste water tank
Data Source
Figure 1
Figure 2
AI summary
In a washing machine or dishwasher, a wastewater tank (6) is connected downstream of the tub (1) for the temporary storage of process water. A heat pump (7-10) extracts heat from the wastewater tank (6) until the wastewater in the tank (6) is partially frozen. At the end of the washing process, the remaining liquid process water in the wastewater tank (6) is replaced by warm process water from the tub (1), thus thawing the ice. This process allows a significant amount of heat to be extracted from the wastewater tank (6) when heating the tub (1).