Dishwasher Heat Exchanger Design for Wastewater Preheating
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Solution Overview
Problem
Existing dishwashing machines do not efficiently recover thermal energy from hot waste water, leading to increased energy consumption in subsequent washing cycles.
Innovation Solution
A dishwashing machine with a heat exchanger that utilizes the drain pump to recirculate hot waste water through a heat exchanger in contact with fresh water, minimizing thermal energy losses and allowing for accurate and stable heat transfer, thereby pre-heating water for subsequent cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If hot waste water is used to pre-heat fresh water through a heat exchanger, then energy consumption is reduced, but thermal energy losses occur during water circulation
Solution Approach 1:
The patent places the heat exchanger directly inside the fresh water tank, creating a localized heat transfer zone where hot waste water circulates through tubes surrounded by fresh water. This local arrangement maximizes thermal contact efficiency and minimizes heat loss to the environment during the pre-heating process.
Solution Approach 2:
The system pre-heats fresh water before it is needed for the washing cycle by circulating hot waste water through the heat exchanger immersed in the fresh water tank. This preliminary heating action reduces the energy required during the actual washing cycle, as the fresh water already starts at a higher temperature.
2Device complexity
If the drain pump is used to recirculate waste water through the heat exchanger, then structural complexity is minimized, but the pump must perform multiple functions
Solution Approach 1:
The drain pump is designed to perform multiple functions: it can pump waste water to the heat exchanger for thermal energy recovery, drain waste water to the discharge pipe, and potentially supply water to a closed-loop drying circuit. This multi-functionality is achieved through a diverter valve that directs the pump output to different destinations based on operational requirements, eliminating the need for separate pumps for each function and thereby reducing structural complexity.
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 reduces energy consumption by pre-heating water, minimizing thermal energy requirements for subsequent washing cycles and maintaining a modular design with minimal structural complexity and cost impact.
Implementation Method 1
a heat exchanger brings hot waste water collected in a sump into thermal contact with fresh water fed by an external water supply. Thermal energy is thus transferred in the form of heat from the hot waste water to the fresh water
Data Source
Figure 1
Figure 2
AI summary
A dishwashing machine comprises a tub (110) that defines a wash space where dishes can be washed, a sump (120) fluidly connected to said tub (110), a drain pump (130) fluidly connected to the sump (120) to discharge waste wash water at the end of a wash cycle, and a water tank (140) configured to receive and store a predefined amount of fresh water from an external water supply. A heat exchanger (160) is arranged inside the water tank (140) and has an inlet (161) fluidly connected with the drain pump (130) and an outlet (162) fluidly connected to the tub (110). A diverter valve (131) is arranged downstream of the drain pump (130) and is configured to selectively direct a flow of water coming from the drain pump (130) to either the heat exchanger (160) or an external discharge pipe.