Absorption Refrigerator Temperature Control for Defrost Off-Time

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Solution Overview

Problem

Absorption refrigerators in vehicles often experience undesirable high internal temperatures due to passive defrost regulation and low ambient temperature conditions, leading to prolonged 'off' times of the refrigeration system, which can result in high temperatures within the refrigerator, especially in low ambient temperatures or when ice builds up on the fins.

Innovation Solution

A temperature control system that includes a combined temperature sensor and heating element, activated by a controller to manage defrosting and low ambient temperature conditions, ensuring the refrigeration system operates efficiently by activating the heating element for predetermined intervals to maintain optimal temperatures and prevent high internal temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If passive defrost regulation is used to turn off the cooling system when internal temperature reaches a low threshold, then energy consumption is reduced, but internal temperature rises to undesirable high levels

Engineering Contradiction:

Improveenergy consumptionVSAvoidinternal temperature

Core Design Contradiction:

Loss of energyVSTemperature

Solution Approach 1:

The heating element is activated in advance during cooling operation to prevent ice buildup on the evaporator fins, rather than waiting for passive defrost to trigger after temperature rises. This preliminary action maintains heat transfer efficiency while avoiding the need for prolonged system shutdowns.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The heating element operates in periodic cycles during the cooling system's operation, providing intermittent heat to prevent ice accumulation without continuously opposing the cooling effect. This periodic heating maintains optimal heat transfer while minimizing energy waste.

Inventive Principle:

Principle #19Periodic action

2Productivity

If the cooling system is deactivated when internal temperature reaches a predetermined low threshold, then cooling efficiency is improved, but the refrigeration system experiences prolonged 'off' times resulting in high internal temperatures

Engineering Contradiction:

Improvecooling efficiencyVSAvoidoff time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The heating element is activated before ice buildup significantly impedes heat transfer, maintaining cooling efficiency by preventing the conditions that would trigger prolonged system shutdowns. This keeps the refrigeration system running continuously with shorter off-times.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The heating element ensures continuous effective cooling by preventing ice accumulation that would force the system to shut down. This maintains the continuity of useful cooling action and reduces the duration of off-periods.

Inventive Principle:

Principle #20Continuity of useful action

3Productivity

If ice builds up on the evaporator fins, then heat transfer efficiency decreases, but the system requires longer defrosting time which increases internal temperature

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoiddefrosting time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The heating element is activated in advance to prevent significant ice buildup on the evaporator fins, maintaining heat transfer efficiency. By addressing ice accumulation early, the system requires minimal or no defrosting time, keeping the refrigeration cycle running continuously.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The heating element, which could be seen as opposing the cooling function, is actually used to prevent harm by removing ice buildup. This converts the heating action into a beneficial defrosting function that protects heat transfer efficiency without requiring separate defrosting cycles.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 effectively prevents high internal temperatures by increasing the 'on' time of the refrigeration system and reducing defrosting time, ensuring the interior remains at a stable low temperature, even in low ambient conditions, thus maintaining the refrigeration efficiency and user comfort.

Implementation Method 1

A temperature sensor senses a temperature within the cabinet

Methodology Applied

Scientific EffectTemperature sensing: Thermistor

Implementation Method 2

A heating element is disposed within the interior volume... The heating element can comprise a resistor

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 3

A cooling system cools the interior volume

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS9250011B2Absorption refrigerator with temperature control

Publication Date: 2016.02.02 THETFORD BV

AI summary

A cooling unit constructed in accordance with one example of the present disclosure includes an outer shell that defines an interior volume. A cooling system cools the interior volume. A temperature sensor senses a temperature within the interior volume. A heating element is disposed within the interior volume. A controller communicates with the temperature sensor and the heating element and activates the heating element based on the temperature satisfying a threshold.