US-12624845-B2 - Air conditioner, method for controlling air conditioner, and recording medium

US12624845B2US 12624845 B2US12624845 B2US 12624845B2US-12624845-B2

Abstract

In an air conditioner, a controller calculates a value of a pressure of a refrigerant when the refrigerant is a saturated liquid at a value of a temperature measured by a second sensor, calculates, based on a value of a pressure or a temperature measured by a third sensor, a value of a pressure at an outlet of an expansion valve, calculates a difference dP1 between a value of a pressure measured by a first sensor and the calculated value of the pressure of the saturated liquid and a difference dP2 between the calculated value of the pressure of the saturated liquid and the value of the pressure at the outlet of the expansion valve, and adjusts, based on a proportion of the calculated difference dP2 to the calculated difference dP1, a degree of opening of the expansion valve.

Inventors

Hironori Hattori
Kojiro MOTOMURA
Takashi Kobayashi
Takuya Kodama

Assignees

MITSUBISHI ELECTRIC CORPORATION

Dates

Publication Date: 20260512
Application Date: 20210924

Claims (15)

1 . An air conditioner, comprising: a refrigerant circuit including a compressor to compress a refrigerant, a condenser to condense the refrigerant ejected from the compressor, a supercooling device to supercool the refrigerant condensed by the condenser, an expansion valve to expand the refrigerant that has passed through the supercooling device, and an evaporator to evaporate the refrigerant expanded by the expansion valve; a first sensor to measure a pressure of the refrigerant compressed by the compressor and yet to be expanded by the expansion valve; a second sensor to measure a temperature of the refrigerant supercooled by the supercooling device and yet to be expanded by the expansion valve; a third sensor to measure a pressure or a temperature of the refrigerant expanded by the expansion valve and yet to be compressed by the compressor; and a controlling circuitry configured to calculate a value of a pressure of the refrigerant when the refrigerant is a saturated liquid at a value of the temperature measured by the second sensor, to calculate, based on a value of the pressure or the temperature measured by the third sensor, a value of a pressure at an outlet of the expansion valve, to calculate a difference dP1 between a value of the pressure measured by the first sensor and the calculated value of the pressure of the saturated liquid and a difference dP2 between the calculated value of the pressure of the saturated liquid and the value of the pressure at the outlet of the expansion valve, and to adjust, based on a proportion of the calculated difference dP2 to the calculated difference dP1, a degree of opening of the expansion valve.
2 . The air conditioner according to claim 1 , wherein the refrigerant circuit further includes a bypass pipe to divert, to a suction port of the compressor, a portion of the refrigerant that has passed through the condenser, the expansion valve includes a bypass expansion valve and a main expansion valve, the bypass expansion valve being located on the bypass pipe and configured to expand the refrigerant, the main expansion valve being configured to receive a portion of the refrigerant that has passed through the condenser and undiverted to the bypass pipe and expand the undiverted portion of the refrigerant, the supercooling device supercools the refrigerant by causing heat exchange between the refrigerant that has passed through the condenser and yet to be diverted to the bypass pipe and the refrigerant expanded by the bypass expansion valve, and the controlling circuitry adjusts, based on the proportion of the calculated difference dP2 to the calculated difference dP1, a degree of opening of either one of the bypass expansion valve and the main expansion valve.
3 . The air conditioner according to claim 2 , wherein the controlling circuitry calculates a parameter K indicating the proportion of the difference dP2 to the difference dP1 using Formula 1 below: K =(dP1+dP 2 )/dP 1 Formula 1, the controlling circuitry determines, by determining whether a value of the calculated parameter K is within a numerical range indicating a distribution of values of the parameter K corresponding to reduced generation of a passage sound of the refrigerant, whether a passage sound of the refrigerant is generated, and the controlling circuitry adjusts the degree of opening of either one of the bypass expansion valve and the main expansion valve when determining that the value of the calculated parameter K is out of the numerical range and a passage sound of the refrigerant is yet to be reduced.
4 . The air conditioner according to claim 3 , wherein the controlling circuitry decreases the degree of opening of the bypass expansion valve when the calculated value of the parameter K is less than a lower limit of the numerical range, and increases the degree of opening of the bypass expansion valve when the calculated value of the parameter K is greater than an upper limit of the numerical range.
5 . The air conditioner according to claim 3 , wherein the controlling circuitry increases the degree of opening of the main expansion valve when the calculated value of the parameter K is less than a lower limit of the numerical range, and decreases the degree of opening of the main expansion valve when the calculated value of the parameter K is greater than an upper limit of the numerical range.
6 . The air conditioner according to claim 2 , wherein the refrigerant circuit includes a connector to allow a portion of the refrigerant excluding the portion diverted to the bypass pipe to flow through a connection pipe connected to the main expansion valve, and the second sensor is located in the connector.
7 . The air conditioner according to claim 1 , wherein the second sensor is located at an inlet of the expansion valve.
8 . The air conditioner according to claim 1 , wherein the first sensor is located at an outlet of the compressor or an inlet of the expansion valve.
9 . The air conditioner according to claim 1 , wherein the third sensor is located at the outlet of the expansion valve to measure a pressure of the refrigerant flowing through the outlet of the expansion valve.
10 . The air conditioner according to claim 1 , comprising: a first storage to store correction data for correcting, based on an installation position of the third sensor, a measurement value of the third sensor, wherein the controlling circuitry calculates, based on the value of the pressure or the temperature measured by the third sensor and the correction data, the value of the pressure at the outlet of the expansion valve.
11 . The air conditioner according to claim 10 , wherein the third sensor is located at the evaporator to measure a pressure of the refrigerant flowing through the evaporator, the correction data is data, corresponding to a pressure loss of the refrigerant from the outlet of the expansion valve to the installation position of the third sensor at the evaporator, for correcting the measurement value of the third sensor, and the controlling circuitry calculates, based on the value of the pressure measured by the third sensor and the correction data, the value of the pressure at the outlet of the expansion valve.
12 . The air conditioner according to claim 10 , comprising: a second storage to store physical property data about the refrigerant flowing through the refrigerant circuit, wherein the third sensor is installed at the evaporator to measure a temperature of the refrigerant flowing through the evaporator, the correction data is data, corresponding to a pressure loss of the refrigerant from the outlet of the expansion valve to the installation position of the third sensor at the evaporator, for correcting the measurement value of the third sensor, and the controlling circuitry calculates, using the value of the temperature measured by the third sensor and the physical property data, a value of a pressure of the refrigerant flowing through the installation position of the third sensor, and calculates, based on the calculated value of the pressure of the refrigerant and the correction data, the value of the pressure at the outlet of the expansion valve.
13 . The air conditioner according to claim 1 , comprising: a storage to store physical property data about the refrigerant flowing through the refrigerant circuit, wherein the controlling circuitry calculates, using the physical property data, a value of a pressure of the refrigerant when the refrigerant is a saturated liquid at the value of the temperature measured by the second sensor, and calculates, based on the physical property data and the value of the pressure or the temperature measured by the third sensor, the value of the pressure at the outlet of the expansion valve.
14 . A method for controlling an air conditioner, the air conditioner including a refrigerant circuit that includes a compressor to compress a refrigerant, a condenser to condense the refrigerant ejected from the compressor, a supercooling device to supercool the refrigerant condensed by the condenser, an expansion valve to expand the refrigerant that has passed through the supercooling device, and an evaporator to evaporate the refrigerant expanded by the expansion valve, the method comprising: measuring a temperature of the refrigerant supercooled by the supercooling device and yet to be expanded by the expansion valve, and calculating a value of a pressure of the refrigerant when the refrigerant is a saturated liquid at a value of the measured temperature; measuring a pressure or a temperature of the refrigerant expanded by the expansion valve and yet to be compressed by the compressor, and calculating, based on a value of the measured pressure or the measured temperature, a value of a pressure at an outlet of the expansion valve; measuring a pressure of the refrigerant compressed by the compressor and yet to be expanded by the expansion valve, and calculating a difference dP1 between a value of the measured pressure and the value of the pressure of the saturated liquid and a difference dP2 between the value of the pressure of the saturated liquid and the value of the pressure at the outlet of the expansion valve; and adjusting, based on a proportion of the calculated difference dP2 to the calculated difference dP1, a degree of opening of the expansion valve.
15 . A non-transitory recording medium storing a program configured to be executed by a computer configured to control an air conditioner, the air conditioner including a refrigerant circuit including a compressor to compress a refrigerant, a condenser to condense the refrigerant ejected from the compressor, a supercooling device to supercool the refrigerant condensed by the condenser, an expansion valve to expand the refrigerant that has passed through the supercooling device, and an evaporator to evaporate the refrigerant expanded by the expansion valve, a first sensor to measure a pressure of the refrigerant compressed by the compressor and yet to be expanded by the expansion valve, a second sensor to measure a temperature of the refrigerant supercooled by the supercooling device and yet to be expanded by the expansion valve, and a third sensor to measure a pressure or a temperature of the refrigerant expanded by the expansion valve and yet to be compressed by the compressor, the program causing the computer to perform operations comprising: calculating a value of a pressure of the refrigerant when the refrigerant is a saturated liquid at a value of the temperature measured by the second sensor, calculating, based on a value of the pressure or the temperature measured by the third sensor, a value of a pressure at an outlet of the expansion valve, and calculating a difference dP1 between a value of the pressure measured by the first sensor and the value of the calculated pressure of the saturated liquid and a difference dP2 between the value of the calculated pressure of the saturated liquid and the value of the pressure at the outlet of the expansion valve; and adjusting, based on a proportion of the calculated difference dP2 to the calculated difference dP1, a degree of opening of the expansion valve.

Description

TECHNICAL FIELD The present disclosure relates to an air conditioner, a method for controlling an air conditioner, and a program. BACKGROUND ART A known air conditioner includes an outdoor unit including a compressor, a condenser, and a supercooling device, and an indoor unit including an expansion valve and an evaporator. In such an air conditioner, the refrigerant may generate a sound when passing through a pipe connecting the condenser in the outdoor unit and an inlet of the expansion valve in the indoor unit. To reduce the sound, the air conditioner may include a controller that adjusts the degree of opening of the expansion valve based on output values from a temperature sensor that measures the temperature of the refrigerant or a pressure sensor that measures the pressure of the refrigerant. For example, Patent Literature 1 describes an air conditioner including an outdoor unit, a supercooling device, and a controller. The outdoor unit includes a bypass pipe that diverts a portion of the refrigerant that has passed through a condenser, a bypass expansion valve located on the bypass pipe, and an outdoor expansion valve located on a pipe that guides, to an outlet of the outdoor unit, the remaining portion of the refrigerant undiverted to the bypass pipe. The supercooling device causes heat exchange between the refrigerant that has passed through the condenser but yet to be diverted to the bypass pipe and the refrigerant expanded by the bypass expansion valve. The controller increases the degree of opening of the bypass expansion valve until the temperature value of the refrigerant measured by a temperature sensor at the inlet of the outdoor expansion valve reaches below the saturated liquid temperature. The air conditioner described in Patent Literature 1 includes an indoor unit including an indoor expansion valve that expands the remaining refrigerant undiverted to the bypass pipe. The controller increases the degree of opening of the outdoor expansion valve until the pressure value of the refrigerant measured by a pressure sensor at the inlet of the indoor expansion valve reaches above the saturated liquid pressure. Patent Literature 2 describes an air conditioner including an outdoor expansion valve located at the same position as the outdoor expansion valve described in Patent Literature 1. The air conditioner includes a controller that calculates a pressure loss of a pipe connecting the outlet of the outdoor unit to the inlet of the indoor unit based on output values from a first pressure sensor that measures the suction pressure of a compressor and a second pressure sensor that measures the ejection pressure of the compressor, and adjusts the degree of opening of the outdoor expansion valve based on the calculated pressure loss. CITATION LIST Patent Literature Patent Literature 1: International Publication No. WO 2016/203624Patent Literature 2: Unexamined Japanese Patent Application Publication No. 2019-20112 SUMMARY OF INVENTION Technical Problem The air conditioner described in Patent Literature 1 includes no sensor that measures the state of the refrigerant such as the temperature or the pressure upstream and downstream from the indoor expansion valve, and cannot accurately determine the state of the refrigerant upstream and downstream from the indoor expansion valve. The air conditioner may thus have difficulty in controlling the degrees of opening of the bypass expansion valve and the outdoor expansion valve precisely. This may not sufficiently reduce generation of a passage sound of the refrigerant passing through the indoor expansion valve. The air conditioner described in Patent Literature 2 includes no sensor that measures the state of the refrigerant such as the temperature or the pressure upstream and downstream from the indoor expansion valve. The air conditioner thus may not sufficiently reduce generation of a passage sound of the refrigerant passing through the indoor expansion valve, as with the air conditioner described in Patent Literature 1. In response to the above issue, an objective of the present disclosure is to provide an air conditioner, a method for controlling an air conditioner, and a program that can sufficiently reduce generation of a passage sound of a refrigerant passing through an expansion valve. Solution to Problem To achieve the above objective, an air conditioner according to an aspect of the present disclosure includes a refrigerant circuit, a first sensor, a second sensor, a third sensor, and a controller. The refrigerant circuit includes a compressor to compress a refrigerant, a condenser to condense the refrigerant ejected from the compressor, a supercooling device to supercool the refrigerant condensed by the condenser, an expansion valve to expand the refrigerant that has passed through the supercooling device, and an evaporator to evaporate the refrigerant expanded by the expansion valve. The first sensor measures a pressure of the refrigerant compressed