WO2022132060A1 - Système de dégivrage - Google Patents

Système de dégivrage Download PDF

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Publication number
WO2022132060A1
WO2022132060A1 PCT/TR2020/051292 TR2020051292W WO2022132060A1 WO 2022132060 A1 WO2022132060 A1 WO 2022132060A1 TR 2020051292 W TR2020051292 W TR 2020051292W WO 2022132060 A1 WO2022132060 A1 WO 2022132060A1
Authority
WO
WIPO (PCT)
Prior art keywords
frost
defrosting system
sensor
evaporator
defrosting
Prior art date
Application number
PCT/TR2020/051292
Other languages
English (en)
Inventor
İsmail LAZOĞLU
Anjum Naeem MALIK
Original Assignee
Koc Universitesi
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koc Universitesi filed Critical Koc Universitesi
Priority to PCT/TR2020/051292 priority Critical patent/WO2022132060A1/fr
Publication of WO2022132060A1 publication Critical patent/WO2022132060A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/02—Detecting the presence of frost or condensate
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/06—Removing frost
    • F25D21/08—Removing frost by electric heating

Definitions

  • the present invention relates to a defrosting system for refrigeration systems to save the wastage of energy during defrosting.
  • Refrigeration systems are an indispensable need of the current era.
  • the refrigeration systems are ubiquitous from food preservation in households and supermarkets to heating ventilation and cooling at a large scale for keeping the ambient temperature down during extreme weather.
  • the refrigeration systems According to the International Institute of Refrigeration (HR, France 2019), the refrigeration systems collectively consume 20% of the total electricity produced in the world. Therefore, improving the energy efficiency of refrigeration systems is of huge importance.
  • Frost's deposition on the evaporator coil of the refrigeration system is one of the bottlenecks in improving the energy efficiency of refrigeration systems.
  • the accumulation of frost on the evaporator coil acts as a thermal resistance during convective heat transfer.
  • Frost deposition also clogs the evaporator coil that results in the drop of the airside pressure drop of the evaporator and thus decreases the cooling capacity of the refrigeration system.
  • the amount of frost deposition on the surface of the evaporator is in direct proportion to the loss of energy. Therefore, to improve the efficiency of the refrigeration system, the removal of frost from the surface of the evaporator becomes inevitable.
  • defrosting systems There are different types of defrosting systems that have been reported in the literature and are being in use nowadays. For example, the reverse cycle defrosting, the hot gas bypass defrosting, and the electrically powered resistive heater defrosting.
  • reverse cycle defrosting a solenoid control valve is used to reverse the flow of the refrigerant that converts the evaporator into the condenser to melt the frost.
  • hot gas bypass defrosting a bypass valve is used to send the hot refrigerant directly into the evaporator rather than passing through the condenser.
  • electrically powered resistive heater defrosting a heating element is attached to the evaporator that transmits the heat through conduction or radiation to melt the frost.
  • the electrically powered resistive heater defrosting is considered the most viable defrosting system by the refrigeration industry.
  • the resistive heater is normally turned-on periodically once in 24 hours and tumed-off either periodically or based on the temperature sensor that monitors the surrounding air temperature during defrosting.
  • periodically controlled defrosting systems are inefficient because the frosting is a random process, and triggering the defrosting system without estimating the amount of deposited frost would result in the waste of energy. Therefore, different frost detection sensors have been reported and currently are being in use.
  • the frost detection sensor monitors the thickness of frost on the surface of the evaporator and turns on the defrosting heater once a frost thickness exceeds the threshold point.
  • frost detection sensor along with an electrically powered resistive heater
  • the heater is activated on-demand based on the amount of frost and deactivated when all the deposited frost melts away.
  • frost on the surface of the evaporator is not uniform. For instance, in a tube-fin type evaporator of a domestic refrigerator, the frost starts to deposit from the top tubing and gradually reaches the bottom tubes. This phenomenon occurs because working fluid enters the evaporator from the top at a very low temperature and exits near the bottom at a significantly different temperature due to heat transfer. Additionally, the frost deposition is mainly dependent on different parameters such as relative humidity, air velocity, the temperature of the surroundings, and the evaporator. Therefore, the thickness of deposited frost varies along the surface of the evaporator.
  • Modem refrigeration systems currently employ a single electrically powered, resistive heater that triggers-on upon the detection of frost by the frost detection sensor and remained on unless the sensor detects the melting of frost on the whole surface of the evaporator.
  • the melting is performed faster on the points where there is a thin layer of frost and slower where there is a thick layer of frost.
  • the heater continues to provide heat to all the surfaces of the evaporator unless all the deposited frost on the evaporator surface will be melted away. This would result in energy loss during defrosting.
  • a patent application numbered US2005189493A1 relates to an optical sensor to detect frost in refrigeration systems. Once a preset amount of frost is detected, the controller triggers the defrost system. In this patent application document, a single defrost system is used as a defrosting system.
  • a patent application numbered CN107514860A relates to a capacitive sensor for detecting frost in refrigeration systems.
  • the sensor detects the presence of frost and measures its thickness, based on the change in total capacitance.
  • the capacitance varies in direct proportion to the amount of frost. They proposed a capacitive sensor to triggers the defrosting system on demand.
  • a US patent document numbered US6415616 B l relates to a defrosting method to defrost the evaporator without wasting energy.
  • An objective of the present invention is to provide a system proposing multiple low power heaters installation on the surface of the evaporator.
  • the control of individual heaters is achieved through individual frost detection sensors that are mounted on the same location where a heater is installed. This localized installation of heaters and sensors would enable the detection and defrost without excessive energy wastage.
  • the industrial appliances in the technical field are using a single defrosting heater that is controlled by either a direct frost detection sensor that detects the presence and measures the amount of frost or indirect sensing of frost by monitoring indirect parameters such as temperature and the pressure variations inside the refrigerator cabin.
  • the frost accumulation surpasses the preset threshold, the defrost system actuates and remains actuated for an extended period. This would result in inefficient defrosting. With the present invention, this inefficiency is eliminated.
  • Figure 1 shows the evaporator coil with multiple frost sensors and defrosting heaters.
  • Figure 2 shows the working principle of a single frost detection sensor and the defrosting heater.
  • the present invention relates to a defrosting system (D) suitable for refrigeration systems comprising evaporator (E) characterizing that the defrosting system (D) comprises
  • At least one control unit (3) for processing the frost detection sensors (1) data and generating control commands to drive the defrost heaters (2).
  • the present invention relates to a defrosting system (D) suitable for refrigeration systems.
  • the defrosting system (D) comprises multiple frost detection sensors (1), at least one defrost heater (2) at the same location of each frost detection sensor (1), and at least one control unit (3) for communication between frost detection sensor (1) and defrost heater (2).
  • the frost detection sensor (1) detects and measures the amount of frost deposited on the surface of the evaporator (E) of the refrigeration system.
  • the frost detection sensor (1) is positioned at various locations on the surface of the evaporator (E).
  • the resistive defrost heater (2) generates heat with the help of the electrical power supplied. In this way, the heat generated is used to remove the deposited frost.
  • the control unit (3) is responsible for the communication between the frost detection sensor (1) and the resistive defrost heater (2).
  • the frost detection sensor (1) is preferably based on optical sensing principle where at least one infrared or ultraviolet or visible light transmitter (4) transmits light on to the surface of the evaporator (E) where frost accumulates and at least one infrared or ultraviolet or visible light receiver (5) receives the reflected light bouncing back from the frost accumulated surface.
  • the output voltage of the receiver (5) changes in direct proportion to the intensity of the received light beam as the intensity of the light is dependent on the thickness of the frost.
  • the difference between the output of the infrared receiver (5) during no-frost and frosting is used to detect the frost.
  • the output of the receiver (5) is calibrated to the amount of frost on the evaporator (E).
  • the frost detection sensor (1) is preferably based on the capacitive sensing principle where the capacitance change is measured in proportion to the amount of deposited frost.
  • Frost has a dielectric constant different than the air or water therefore the frost deposition has a direct effect on the change in capacitance.
  • the deposition of frost disturbs the electric field between the electrodes of the capacitor and would result in the capacitance change.
  • This change in capacitance is in direct proportion to the amount of frost on the evaporator (E).
  • the capacitance change is calibrated to the frost thickness.
  • the Frost detection sensor (1) comprises at least one capacitive sensor for measuring the change in capacitance to the amount of frost.
  • the capacitive sensor can be configured in a parallel electrode configuration or a comb shape electrode configuration.
  • the frost detection sensor (1) comprises at least one resistive sensor.
  • the resistive sensor can be configured in the parallel placed electrode configuration.
  • the working principle of the resistive sensor is varying resistance based on the presence of frost on the sensor electrodes.
  • the potential difference is applied between the electrodes. When the frost starts to deposit the potential difference changes because of the change in resistance between the electrodes. This change is a potential difference that can be used as a deciding factor to detect the presence of frost.
  • the defrost heater (2) comprises at least one conducting element having an electrical resistance. When the potential difference is applied across the conducting element, the current begins to flow through the conductor. As a result of the flowing current, heat is produced by the conductor. This process is known as Joule heating.
  • the defrost heater (2) in the defrosting system (D) is a low-power electrical resistive defrost heater (2) for defrosting purposes. To defrost efficiently, multiple low power electrical resistive defrost heaters (2) are installed on various locations of the evaporator (E). Based on the thickness of frost in a certain region of the evaporator (E), the electrical resistive defrost heaters (2) installed in that region are triggered-on when the thickness of the frost exceeds the set point.
  • the electrical resistive defrost heater (2) triggers-off when the frost in that region melts ways.
  • the defrost heater (2) can be either a sheathed type or a glass tube type.
  • Sheathed type heater is a type of electrically powered resistive heater.
  • the resitive heating element is capsulated in a meatlic pipe. When powered, heat is generated by Joule’s effect.
  • Glass tube type heater is different than resistive heater, as it emits infrared radiations that produce heat.
  • both sheathed as well as glass tube heaters are an alternate to resitive type heaters that we are proposing in this invention.
  • the current refrigeration systems in the technical field employ a single heater to completely remove the frost from the evaporator (E), thus consumes more power.
  • the defrost heaters (2) will consume significantly less power as compared to a single high-powered heater. For example, a single heater consumes 150 Watts of power and we are replacing this single heater with multiple defrost heaters (2) (each consumes 12 Watts of power).
  • the control unit (3) receives the data from multiple frost detection sensors (1) and continuously compares it with the preset threshold values for different frost thickness levels. When the output of any of the frost detection sensors (1) crosses the preset threshold, the control unit (3) triggers the respective defrost heater (2) on that location to tum-on.
  • the control unit (3) comprises at least one microcontroller or microprocessor or field-programmable gate array for analyzing the frost detection sensor (1) data.
  • frost detection sensors (1) can be used to detect the frost such as temperature sensor, pressure sensor, inductance sensor, an impedance sensor, laser displacement gauge sensor, fiber optic sensor, and piezoelectric sensor in the defrosting system (D).
  • the evaporator (E) is preferably a tube-fin type evaporator (E).
  • the frosting is a complex random process that depends on various parameters. Therefore, the thickness of frost on the surface of the evaporator (E) is not uniform. The thickness of frost on the top side of the evaporator (E) would be significantly different than the bottom of the evaporator (E). Therefore, the defrosting heater takes less time to melt the frost on the bottom side of the evaporator (E) as compared to the top side. In these conditions, choosing a single threshold value to trigger defrosting would result in energy loss. Hence, multiple threshold values for each defrost heater (2) is chosen, based on the frost detection sensor (1) response. This would result in triggering-on/off of only those defrost heaters (2) where the frost thickness value is beyond the threshold value.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Defrosting Systems (AREA)

Abstract

La présente invention concerne un système de dégivrage (D) destiné à des systèmes de réfrigération pour économiser le gaspillage d'énergie pendant le dégivrage. Le système de dégivrage (D) comprend de multiples capteurs de détection de givre (1) sur différentes positions de la surface de l'évaporateur (E) pour détecter la présence et mesurer la quantité de givre, au moins un dispositif de chauffage de dégivrage (2) dans la même position avec chaque capteur de détection de givre (1) pour faire fondre le givre et au moins une unité de commande (3) pour traiter les données de capteurs de détection de givre (1) et générer des commandes de contrôle pour entraîner les dispositifs de chauffage de dégivrage (2).
PCT/TR2020/051292 2020-12-14 2020-12-14 Système de dégivrage WO2022132060A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/TR2020/051292 WO2022132060A1 (fr) 2020-12-14 2020-12-14 Système de dégivrage

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/TR2020/051292 WO2022132060A1 (fr) 2020-12-14 2020-12-14 Système de dégivrage

Publications (1)

Publication Number Publication Date
WO2022132060A1 true WO2022132060A1 (fr) 2022-06-23

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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2019E (fr) 1903-11-24 Gustave Bouquillon Bandage pneumatique ferré antidérapant à chaine amovible
JPH01239370A (ja) * 1988-03-17 1989-09-25 Sanden Corp 冷凍・冷蔵ショーケースの除霜制御方法
JP2000074546A (ja) * 1998-09-01 2000-03-14 Denso Corp 冷凍機の除霜制御装置
JP2000121233A (ja) * 1998-10-20 2000-04-28 Toshiba Corp 冷凍冷蔵庫
US6415616B1 (en) 1999-09-03 2002-07-09 Lg Electronics, Inc. Method for controlling defrost heater of refrigerator
US20050189493A1 (en) 2004-01-07 2005-09-01 Alan Bagley Optical frost sensor
US20120055181A1 (en) * 2010-09-02 2012-03-08 Samsung Electronics Co., Ltd. Cooling system and defrosting control method thereof
JP2013079783A (ja) * 2011-10-05 2013-05-02 Mitsubishi Electric Corp 冷却装置
CN107514860A (zh) 2017-09-06 2017-12-26 芯海科技（深圳）股份有限公司 一种电容式冰箱凝霜传感器检测电路
US20200173708A1 (en) * 2018-11-28 2020-06-04 Samsung Electronics Co., Ltd Refrigerator and control method thereof

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2019E (fr) 1903-11-24 Gustave Bouquillon Bandage pneumatique ferré antidérapant à chaine amovible
JPH01239370A (ja) * 1988-03-17 1989-09-25 Sanden Corp 冷凍・冷蔵ショーケースの除霜制御方法
JP2000074546A (ja) * 1998-09-01 2000-03-14 Denso Corp 冷凍機の除霜制御装置
JP2000121233A (ja) * 1998-10-20 2000-04-28 Toshiba Corp 冷凍冷蔵庫
US6415616B1 (en) 1999-09-03 2002-07-09 Lg Electronics, Inc. Method for controlling defrost heater of refrigerator
US20050189493A1 (en) 2004-01-07 2005-09-01 Alan Bagley Optical frost sensor
US20120055181A1 (en) * 2010-09-02 2012-03-08 Samsung Electronics Co., Ltd. Cooling system and defrosting control method thereof
JP2013079783A (ja) * 2011-10-05 2013-05-02 Mitsubishi Electric Corp 冷却装置
CN107514860A (zh) 2017-09-06 2017-12-26 芯海科技（深圳）股份有限公司 一种电容式冰箱凝霜传感器检测电路
US20200173708A1 (en) * 2018-11-28 2020-06-04 Samsung Electronics Co., Ltd Refrigerator and control method thereof

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