Warewasher Heat Recovery Rinse Mixing for Fast Startup
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Solution Overview
Problem
Commercial warewashers with heat recovery systems face challenges in achieving desired operating temperatures during startup, as the exhaust system temperature is initially insufficient, leading to excessive time required for the water to reach the desired rinse temperature.
Innovation Solution
A heat recovery system with a control valve that selectively supplements water from a hot water source to the final rinse system, ensuring the water reaches the desired temperature by mixing hot water with the heated water from the heat recovery system, even during startup or when the heat recovery efficiency is low.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a heat recovery system is used to transfer heat from exhaust air to cold water, then energy efficiency is improved and operating costs are reduced, but during startup the exhaust system temperature is insufficient leading to excessive time required to reach desired rinse temperatures
Solution Approach 1:
A hot water storage tank is pre-filled with hot water from a hot water source before the heat recovery system becomes operational. This preliminary action ensures that hot water is immediately available for the final rinse system during startup, eliminating the warmup delay while the heat recovery system gradually heats the water supply for subsequent operation
Solution Approach 2:
A three-way mixing valve is introduced as an intermediary device that blends hot water from the storage tank with water from the heat recovery system. This mediator allows the system to deliver hot water immediately during startup by mixing pre-heated water with the cooler water from the heat recovery system, then gradually transition to using only heat recovery water once the exhaust system reaches sufficient temperature
2Loss of time
If hot water from a hot water source is mixed with water from the heat recovery system, then the desired rinse temperature is achieved quickly, but the system complexity increases with additional valves and control mechanisms
Solution Approach 1:
The system employs temperature sensors and a controller that automatically monitor water temperature and exhaust system temperature, then autonomously control the three-way mixing valve to blend hot water from the storage tank with water from the heat recovery system. This self-service automation eliminates the need for manual intervention and simplifies operation despite the added hardware complexity
Solution Approach 2:
The control system dynamically adjusts the mixing ratio of hot water from the storage tank and water from the heat recovery system based on real-time temperature parameters. As the exhaust system temperature increases over time, the controller progressively reduces the proportion of stored hot water and increases the proportion of heat recovery water, optimizing the blend to achieve target temperature while adapting to changing system conditions
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 the time needed for the final rinse water to reach the desired temperature, ensuring efficient operation and energy savings while maintaining high-temperature rinse performance, even during initial start-up or when the heat recovery system's efficiency is decreased.
Implementation Method 1
A heat recovery system is located between the final rinse system and the cold water source. The heat recovery system transfers heat from the exhaust air to the cold water provided from the cold water source.
Implementation Method 2
A valve associated with the hot water source selectively supplements the water exiting the heat recovery system with hot water from the hot water source.
Data Source
AI summary
A warewasher for washing wares includes a housing defining an internal space with at least one spray zone for washing wares. A liquid delivery system provides a spray of liquid within the spray zone. A tank includes an inlet that is connected to a hot water source for filling the tank with hot water. The liquid delivery system receives water from the tank. An exhaust vents heated air from the housing. A final rinse system is connected to a cold water source. A heat recovery system is located between the final rinse system and the cold water source. The heat recovery system transfers heat from the exhaust air to the cold water provided from the cold water source. A valve associated with the hot water source selectively supplements the water exiting the heat recovery system with hot water from the hot water source.