Reducing Agent Tank Heating Layout for Freeze-Thaw Delivery
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Solution Overview
Problem
Existing systems for delivering liquid reducing agents, such as aqueous urea solutions, to exhaust-gas flows in internal combustion engines face challenges with freezing, leading to inefficient thawing and removal, particularly at low temperatures, resulting in incomplete delivery and vacuum issues during thawing.
Innovation Solution
A tank and delivery unit configuration with a chamber on the tank bottom housing a heater, thermal insulation, and a self-regulating heating system that ensures targeted and efficient thawing of frozen reducing agents, preventing local hot spots and facilitating bubble-free delivery, while also incorporating a return line to manage ice formation and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heater is placed on the tank bottom to thaw frozen reducing agent, then the reducing agent at the bottom can be thawed, but a thick shell of ice remains above the removal point and vacuum formation prevents pump operation
Solution Approach 1:
The heating strategy transitions from a single-point heat source at the tank bottom to a multi-dimensional approach using multiple heaters positioned at different locations (bottom, side walls, and potentially top) of the tank. This spatial distribution of heat sources in multiple dimensions enables comprehensive thawing of ice throughout the entire tank volume, preventing the formation of a thick ice shell that would block delivery
Solution Approach 2:
The heating system is segmented into multiple independent heating zones with separate heaters positioned at different locations within the tank. Each heater can be controlled independently to address localized freezing conditions, ensuring complete thawing coverage and preventing vacuum formation that would compromise delivery reliability
2Productivity
If concentrated heat is introduced to quickly thaw frozen reducing agent, then thawing speed increases, but local hot spots with surface temperatures greater than 90° C. are created
Solution Approach 1:
The heating system divides the total heating power into multiple segments through several heaters distributed at different locations in the tank. Each heater provides moderate heat to its local zone, collectively achieving rapid thawing while preventing any single location from developing dangerous hot spots exceeding 90° C.
Solution Approach 2:
The heating strategy applies local quality control by positioning heaters to provide targeted heat to specific frozen zones while maintaining temperature uniformity throughout the tank. This ensures each local region receives appropriate heat intensity for efficient thawing without creating excessive temperature gradients or hot spots
3Quantity of substance
If the delivery unit is positioned close to the tank bottom for extracting liquid reducing agent, then complete tank emptying is enabled, but vacuum formation occurs during suction that pumps cannot overcome
Solution Approach 1:
The system performs preliminary heating and thawing of the reducing agent before extraction begins. By ensuring the liquid is fully thawed and fluid throughout the tank, particularly at the bottom where the delivery unit is positioned, the system prevents vacuum formation during suction, allowing complete tank emptying without exceeding pump capabilities
Solution Approach 2:
The heating system acts as an intermediary that prepares the reducing agent in a fully liquid state before extraction. This thermal preparation eliminates the formation of ice blocks or vacuum conditions during pumping, enabling complete and reliable tank emptying
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 solution enables reliable and efficient thawing of frozen reducing agents, ensuring complete delivery to the exhaust-gas flow, reducing energy consumption, and preventing vacuum formation during thawing, thus maintaining system functionality and reducing maintenance complexity.
Implementation Method 1
a chamber (9) formed off-center on the tank bottom (5), with at least one heater (29)
Implementation Method 2
includes insulation and self-regulating heating elements to ensure efficient thawing
Implementation Method 3
targeted and sufficient thawing of frozen reducing agent is already achieved shortly after starting
Data Source
AI summary
A device includes at least one tank having a tank bottom and a delivery unit for a liquid. The delivery unit is disposed in a chamber on the tank bottom and the chamber includes at least one heater. The tank preferably has at least one local ventilation heater extending from a discharge for liquid on the tank bottom over at least one tank side to the vicinity of a tank top.