Continuous-Flow Heater Start-Up Temperature Compensation

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Solution Overview

Problem

Continuous-flow heaters in beverage vending machines face challenges in maintaining consistent liquid dispensing temperatures due to start-up behavior issues, leading to temperature fluctuations and potential overheating, especially when switching on for the first time or during initial liquid withdrawal.

Innovation Solution

The method involves compensating for the start-up behavior by accounting for the inlet and residual liquid temperatures in the heating channel sections, using a return line to maintain a consistent temperature setpoint, and adjusting heating segments to ensure the desired temperature is reached without wasting liquid, allowing for precise temperature control during liquid dispensing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the heating system is switched on with a time delay before starting the pump to ensure target temperature from the start, then the liquid dispensing temperature is improved, but liquid overheating and evaporation occur

Engineering Contradiction:
Improveliquid dispensing temperatureVSAvoidoverheating and evaporation
Core Design Contradiction:
TemperatureVSObject-generated harmful factors

Solution Approach 1:

The heating element is activated before the liquid flow starts, pre-heating the heating channel and any residual liquid. This preliminary action ensures that when liquid flows through, it immediately receives the required thermal energy, achieving target temperature without needing excessive heating power that would cause overheating and evaporation.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts heating power based on operational state (cold start, warm start, continuous operation). By changing the heating parameter according to the current temperature of the heating channel and residual liquid, the system avoids applying full power when unnecessary, thus preventing overheating and evaporation while ensuring target temperature is reached.

Inventive Principle:
Principle #35Parameter changes

2Use of energy by moving object

If the heating system is only switched on from a certain water flow threshold to avoid overheating, then energy consumption is reduced, but the liquid remains cold when threshold is not reached

Engineering Contradiction:
Improveenergy consumptionVSAvoidliquid dispensing temperature
Core Design Contradiction:
Use of energy by moving objectVSTemperature

Solution Approach 1:

The heating system transitions from a static on/off control based on flow threshold to a dynamic control that continuously adjusts heating power based on real-time temperature feedback from the heating channel. This allows the system to apply minimal heating when flow is low (saving energy) while ensuring temperature requirements are met when flow increases.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

Temperature sensors monitor the heating channel temperature and provide feedback to the control unit. The control unit uses this feedback to adjust heating power dynamically, reducing energy consumption when heating is not needed while ensuring target temperature is achieved when liquid flow requires heating.

Inventive Principle:
Principle #23Feedback

3Stability of the object's composition

If the discharge line section is rinsed with unheated liquid after each liquid removal to compensate start-up behavior, then temperature consistency is improved, but liquid waste increases

Engineering Contradiction:
Improvetemperature consistencyVSAvoidliquid waste
Core Design Contradiction:
Stability of the object's compositionVSLoss of substance

Solution Approach 1:

Instead of discarding the rinsing liquid that flows through the heating channel during startup compensation, the system redirects it back to the water supply line. This recovering action allows the liquid to be reused in subsequent dispensing operations, eliminating waste while maintaining temperature consistency through the rinsing process.

Inventive Principle:
Principle #34Discarding and recovering

4Measurement precision

If a return line is used to feed back liquid to the flow heater to maintain temperature setpoint, then temperature control precision is improved, but device complexity increases

Engineering Contradiction:
Improvetemperature control precisionVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The return line serves multiple functions: it acts as a temperature feedback pathway for precise control, a rinsing pathway for startup compensation, and a liquid recovery pathway to prevent waste. By making the return line multi-functional, the system achieves precise temperature control without adding separate dedicated components for each function, thus limiting the increase in device complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 approach ensures that the liquid is dispensed at the desired target temperature consistently, preventing overheating and maintaining temperature stability throughout the dispensing process, whether for brewing tea or espresso, while minimizing liquid waste.

Implementation Method 1

a continuous-flow heater based on a bare wire heating system

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the liquid flowing through the flow heater is fed back to the flow heater at the beginning of the liquid withdrawal via a valve and a return line

Methodology Applied
Scientific EffectFluid flow:

Implementation Method 3

a pump (2), a heating channel section (3) and a valve (4)

Methodology Applied
Scientific EffectPumping: Pump

Data Source

PatentEP2425185B1Method for controlling a continuous flow heater
Publication Date: 2015.01.21 WMF WURTTEMBERGISCHE METALLWARENFABRIK AG
  • EP2425185B1 patent drawingFigure 1~3

AI summary

The invention relates to a method for compensating the starting temperature of a continuous flow heater (1), especially for automatic drinks machines comprising a blank resistance wire system. According to said method, a liquid flowing through the continuous flow heater (1) is heated to a desired nominal temperature, taking into account the admission temperature and the quantity of liquid remaining in the heating channel section (3) or in an outflow line after each liquid discharge.