Parallel Heat Exchanger Tankless Heaters for High Turndown
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Solution Overview
Problem
Existing water heating systems face challenges with high installation complexity, large footprint, and single-point failures due to the need for multiple heat exchangers and complex plumbing, which limits turndown ratios and increases costs.
Innovation Solution
A multi-heat exchanger system with independently controlled heat exchangers connected in parallel, featuring a recirculation pump and modulating valve to manage flow and prevent cavitation, allowing for a high turndown ratio and simplified installation, with a shared exhaust manifold and reduced material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple water heaters are networked together to increase heating capacity, then the total heating power is improved, but the installation complexity and plumbing requirements increase significantly
Solution Approach 1:
The patent combines multiple heat exchangers into a single integrated water heater unit with a shared control system and common plumbing connections. This merging approach achieves the heating capacity of multiple units while eliminating the need for complex networking plumbing, as all heat exchangers share common water inlet/outlet connections and a unified control system coordinates their operation.
Solution Approach 2:
The control system is designed to universally manage multiple heat exchangers through a single interface, making the system multi-functional. The controller can selectively activate individual heat exchangers based on demand, allowing the same physical unit to provide varying heating capacities without requiring different installation configurations.
2Reliability
If each water heater is individually plumbed to cold water supply and output lines, then each unit operates independently, but the amount of plumbing work and pipe fittings increases significantly
Solution Approach 1:
Multiple heat exchangers share common plumbing connections including a single cold water inlet, hot water outlet, and venting system. This merging of plumbing requirements dramatically reduces the amount of piping and fittings needed compared to installing multiple separate water heaters, while the internal configuration maintains independent operation of each heat exchanger.
3Device complexity
If a single heat exchanger is used to simplify the system, then the device complexity is reduced, but the turndown ratio is limited and single-point failures can shut down the entire system
Solution Approach 1:
The water heater incorporates multiple discrete heat exchangers within a single unit, each capable of independent operation. This segmentation allows the system to achieve high turndown ratios by selectively activating individual heat exchangers based on demand, while maintaining system simplicity through shared plumbing and control. The segmented design also eliminates single-point failures, as remaining heat exchangers can continue operating if one fails.
4Adaptability or versatility
If multiple modulating systems are used to achieve high turndown ratios, then the adaptability is improved, but the control system complexity increases
Solution Approach 1:
A single universal control system manages multiple heat exchangers through standardized interfaces and communication protocols. The controller can selectively modulate each heat exchanger's output and coordinate their combined operation to achieve high turndown ratios, while presenting a simplified single-point interface for system control. This universal approach avoids the need for separate control systems for each heat exchanger.
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 system achieves a turndown ratio of up to 33.3:1, reduces installation complexity, and minimizes the risk of single-point failures, while maintaining temperature stability and reducing energy waste through efficient recirculation and bypass flow management.
Implementation Method 1
a plurality of heat exchangers fluidly connected in parallel, each of the plurality of heat exchangers including a fluid conductor
Implementation Method 2
a pump disposed downstream from the first location on the inlet conductor, wherein the pump is disposed upstream from the plurality of heat exchangers to prevent cavitation
Implementation Method 3
the auxiliary conductor including a modulating valve; and wherein the modulating valve and the pump cooperate to cause a recirculation flow
Data Source
AI summary
An on-demand high volume capable fluid heating system for supplying a total heating power at a turndown ratio and a total flowrate of a fluid supply, the fluid heating system comprising a plurality of heat exchangers fluidly connected in parallel, each of the plurality of heat exchangers comprising: a fluid conductor, wherein each of the plurality of heat exchangers contributes to the total heating power and a portion of the total flowrate of the fluid supply through the fluid conductor; an inlet conductor configured to connect the fluid supply to the plurality of heat exchangers; an outlet conductor configured for receiving the fluid supply downstream of the plurality of heat exchangers; an auxiliary conductor connecting the inlet conductor at a first location and the outlet conductor, the auxiliary conductor comprising a modulating valve; and a pump disposed downstream from the first location on the inlet conductor.