Design and selection method of frost control type air source heat pump suitable for different regions

Abstract

A design and selection method for defrosting air source heat pumps applicable to different regions, belonging to the field of defrosting technology and design selection for air source heat pumps. It includes the following steps: Temperature drop ΔT of a conventional air source heat pump. a Achieves anti-frost efficacy at temperatures below 6℃; ΔT a When the temperature is above 6℃, a defrosting heat pump should be selected; when 6 < ΔT a When ≤8, select a defrosting heat pump with CICO=8; when 8 < ΔT a When ≤10, select a defrosting heat pump with CICO=10; when 10<ΔT a When selecting a defrosting heat pump with CICO = 12, calculate the equivalent temperature drop ΔT between the defrosting and defrosting phases of the defrosting air source heat pump under this CICO. a Verify whether the selected defrosting air source heat pump meets the defrosting efficiency requirements. If it does not meet the requirements, ΔT a If the temperature is less than 6°C, a new air source heat pump CICO should be selected; until the corresponding region meets the defrosting efficiency, which is the design and selection of a defrosting air source heat pump; this invention is applicable to different regions and different climate conditions.

Description

Technical Field

[0001] This invention relates to a design and selection method for frost-suppressing air source heat pumps applicable to different regions, belonging to the field of air source heat pump frost suppression technology and design selection. Background Technology

[0002] Air source heat pumps, as a low-grade renewable energy technology powered by electricity, have become the preferred measure for the low-carbon transformation of heating models in my country due to their energy-saving and environmental advantages. In recent years, air source heat pumps have been included in the category of renewable energy technologies by countries such as the EU, Japan, and China, and are also the most common type of heat pump in Europe. Driven by the "Clean Heating Plan for Northern Regions," air source heat pumps, with their inherent advantages, have become one of the most suitable alternatives to coal-fired heating and have been widely used in northern my country. Furthermore, with the increasing demand for indoor thermal comfort and the growing emphasis on winter indoor heating in southern regions, air source heat pumps have also become a suitable technology for addressing heating needs in these areas. As a key technology for heating electrification, air source heat pumps have broad application prospects in many regions of my country.

[0003] In actual operation, air source heat pumps face varying degrees of frosting problems in different regions, with the most severe frosting occurring in high-humidity areas. Statistics show that over 90% of cities in my country experience frosting more than 50% of the heating season. Once frosting occurs, heating capacity decreases by 30% to 55%, and the unit's coefficient of performance (COP) drops by 20% to 50%. Therefore, it is urgent to improve the frosting resistance of air source heat pumps to ensure their operational performance.

[0004] Chinese patent CN109598036A (Beijing University of Technology) discloses a design method for a frost-suppressing air source heat pump, proposing constitutive configuration parameters that can quantify the frost-suppressing capability of the air source heat pump. These parameters include four parameters: the outdoor heat exchanger area, the outdoor fan airflow, the compressor frequency, and the stroke volume. A larger constitutive configuration parameter indicates a lower frost rate and stronger frost-suppressing capability. During the R&D and design phase of air source heat pumps, the frost-suppressing capability can be increased by adjusting the outdoor heat exchanger area and fan airflow. However, my country has a vast territory with complex and varied climates across different regions, resulting in significant differences in frost conditions and the required frost-suppressing capabilities for air source heat pumps. This makes it difficult to rationally design and select frost-suppressing air source heat pumps, hindering the sustainable development of the air source heat pump industry.

[0005] Therefore, scientifically designing and selecting frost-suppressing air source heat pumps for different regions is key to the efficient application and development of this technology across all regions of my country. Summary of the Invention

[0006] This invention addresses the problem of not being able to design and select defrost-type air source heat pumps for different regions. It develops a design and selection method for defrost-type air source heat pumps applicable to different regions. This method comprehensively considers the environmental conditions during the heating season in different regions and the heating performance of air source heat pumps with different defrost capabilities, and designs and selects defrost-type air source heat pumps as needed.

[0007] The technical solution adopted by this invention to solve the technical problem is: a design and selection method for frost-suppressing air source heat pumps applicable to different regions, comprising the following steps:

[0008] (1) Define the defrosting efficiency of air source heat pumps. Integrate the multi-dimensional coupling factors of temperature and humidity, "T..." a -RH” is reduced to “equivalent temperature drop ΔT during defrosting” a "Using a single factor to evaluate the impact of defrosting on the performance of air source heat pumps, according to the 'Energy Efficiency Limits and Energy Efficiency Grades for Air Source Heat Pump Units at Low Ambient Temperatures,' the classification standard for the defrosting demand evaluation index of air source heat pumps is the average defrosting equivalent temperature drop ΔT of conventional air source heat pump units (air source heat pump units without defrosting performance) during the heating season in that city." a In short, the temperature drop ΔT of a conventional air source heat pump a It achieves anti-frost efficacy at temperatures below 6℃;

[0009] (2) Determine whether there is a need for frost suppression in different regions; based on hourly meteorological data of a typical meteorological year, calculate the average ΔT for conventional air source heat pumps (constitutive configuration parameter CICO = 6) during the heating season for the corresponding regions. a When the calculated temperature is greater than 6°C, it is determined that a defrosting air source heat pump is needed in this region.

[0010] (3) Define the threshold range for anti-frost demand; when 6 < ΔT a When ≤8, select a defrosting air source heat pump with CICO=8; when 8 < ΔT a When ≤10, select a defrosting air source heat pump with CICO=10; when 10<ΔT a When choosing a defrosting air source heat pump with CICO=12, select one.

[0011] (4) Calculate the defrosting effect of the selected defrosting air source heat pump in step (3); based on the selected defrosting air source heat pump CICO, calculate the average defrosting equivalent temperature drop of the defrosting air source heat pump during the heating season under this CICO, i.e., the defrosting equivalent temperature drop ΔT of the defrosting air source heat pump. a `;

[0012] (5) Verify whether the defrosting air source heat pump selected in step (3) meets the defrosting energy efficiency requirement. If it does not meet the requirement, the average defrosting equivalent temperature drop ΔT during the heating season is not met. aIf the temperature is ≤6℃, return to step (3) and reselect the air source heat pump CICO;

[0013] (6) Until the corresponding region meets the defrosting energy efficiency, then output the CICO of the air source heat pump selected for the corresponding region, which is the design and selection of the defrosting air source heat pump.

[0014] The ΔT corresponding to the above steps a and ΔT a The determination of ` is carried out using the following steps:

[0015] Combination Figure 1 Under non-frost conditions, when the outdoor ambient temperature T a Below the nominal operating ambient temperature T an At the same time, the heating capacity of a conventional air source heat pump also decreases to Q as the outdoor temperature decreases. h1 The heating capacity is lower than the nominal operating condition Q. hn ,like Figure 1 As shown at point A, based on measured data, a conventional air source heat pump operates at an ambient temperature of T. a Heating capacity Q during frost-free operation h1 It can be calculated according to formula (1):

[0016]

[0017] With a constant ambient temperature, as the relative humidity (RH) increases, the performance of a conventional air source heat pump is affected by defrosting when entering frosting conditions. The heating capacity of the conventional air source heat pump decreases to Q. h2 ,like Figure 1 As shown at point B, this part of the performance loss ΔQ RH (△Q RH =Q h1 -Q h2 This is caused by the influence of relative humidity. According to measured data, conventional air source heat pumps operate at an ambient temperature of T... a The heating capacity Q during operation under frosting conditions with a relative humidity of RH h2 The formula for calculation is as follows (2):

[0018] Q h2 =[0.311T a +0.043T a 2 +0.005T a 3 -(0.783-1.072×10 -4 T a 3 )RH 0.846 -1.647]×Q hn (2)

[0019] The unit performance loss ΔQ caused by defrosting RH The loss is calculated based on the outdoor ambient temperature, as shown in formula (3):

[0020]

[0021] Performance loss ΔQ caused by defrosting process RH The difference between the unit's performance under frost-free and frost-covered conditions when the outdoor ambient temperature remains constant can be calculated using formula (4):

[0022] △Q RH =Q h1 -Q h2 (4)

[0023] Ultimately, the equivalent temperature drop ΔT during defrosting of a conventional air-source heat pump can be obtained. a The calculation formula is shown in (5):

[0024]

[0025] A higher constitutive parameter CICO for an air source heat pump indicates stronger defrosting capability, less performance loss due to defrosting under the same operating conditions, and a lower equivalent temperature drop ΔT during defrosting. a The smaller.

[0026] Under frosting conditions, defrosting air source heat pumps experience less reduction in heating capacity compared to conventional air source heat pumps, such as... Figure 2 As shown, the frost loss coefficient of a conventional air source heat pump is ε1, and the frost loss coefficient of an anti-frost unit is ε2. Through mathematical analysis, the relationship between the two loss coefficients is obtained as follows:

[0027] ε2=ε1×β (6)

[0028] In the formula: β is the correction factor for frost loss in air source heat pumps;

[0029] Performance tests were conducted on six air source heat pumps with different constitutive configuration parameters (CICO) at standard frosting condition 2 / 1℃. By analyzing the frosting loss for each heating cycle, the relationship between the frosting loss coefficients of air source heat pumps with different CICOs was obtained. Finally, a nonlinear regression fitting method was used, such as... Figure 3 As shown, the relationship between the frost loss correction coefficient and CICO is obtained, as shown in equation (7).

[0030] β=-0.376×ln(CICO)+1.664 (7)

[0031] Finally, substituting β into the performance model of a conventional air source heat pump under frost conditions, we can obtain the results for the anti-frost air source heat pump with constitutive parameters CICO and ambient temperature T. a The heating capacity Q during operation under frosting conditions with a relative humidity of RH h The formula that can be calculated is as shown in (8):

[0032] Q h ′={0.854e 0.023Ta ×(0.376×ln(CICO)-0.664)+(-0.376×ln(CICO)+1.664)×[0.311T a +0.043T a 2 +0.005T a 3 -(0.783-1.072×10 -4 T a 3 )RH 0.0846 -1.647]}Q hn (8)

[0033] Performance loss ΔQ caused by defrosting process RH The difference between the unit's performance under frost-free and frost-covered conditions when the outdoor ambient temperature remains constant can be calculated using formula (9):

[0034] ΔQ RH ′=Q h1 -Q h ′ (9)

[0035] The equivalent temperature drop ΔT of defrosting in a defrosting-type air source heat pump can be obtained. a The formula for calculating ` is shown in (10):

[0036]

[0037] The beneficial effects of the present invention are: (1) It has good versatility and is applicable to different regions and different climate conditions; (2) It can scientifically and rationally select anti-frost air source heat pumps; (3) It reduces the performance loss of air source heat pumps caused by frost and promotes the sustainable development of air source heat pump technology. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating a method for reducing the multidimensional coupling factors of temperature and humidity to an equivalent temperature drop during defrosting.

[0039] Figure 2 This is a schematic diagram of the defrosting process of an air source heat pump with different defrosting performance.

[0040] Figure 3This is a schematic diagram showing the relationship between the frost loss correction factor and CICO.

[0041] Figure 4 This is a flowchart illustrating the design and selection method for a frost-suppressing air source heat pump applicable to multiple regions. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the present invention is not limited to the following embodiments.

[0043] Example 1 – Taking Shanghai as an example

[0044] (1) Determine whether there is a need for frost suppression in Shanghai. Based on the hourly temperature T during the heating season of a typical meteorological year in Shanghai. a Calculate the average ΔT during the heating season based on the humidity (RH). a The calculation formula is as follows:

[0045]

[0046] The calculated hourly defrosting equivalent temperature drop time interval for the heating season is 1 hour, and its average value is ΔT. a =10.5℃>6℃, indicating that there is a need for frost suppression in Shanghai.

[0047] (2) Based on the defined frost suppression demand threshold range, because ΔT a =10.5℃>10℃, so a defrosting air source heat pump with CICO=12 is selected.

[0048] (3) Calculate the hourly equivalent temperature drop ΔT between defrosting and frost-free operation during the heating season for a defrosting air source heat pump with CICO = 12. an The calculation formula is as follows:

[0049]

[0050] The calculated hourly defrosting equivalent temperature drop time interval for the heating season is 1 hour, and its average value is ΔT. an =5.5.

[0051] (4) Verify whether the selected air source heat pump meets the defrosting efficiency requirement, because ΔT an =5.5≤6, which meets the condition, so Shanghai selects the defrosting air source heat pump with CICO=12.

Claims

1. A design and selection method for frost-suppressing air source heat pumps applicable to different regions, characterized in that, Includes the following steps: (1) Define the frost control energy efficiency of air source heat pump; According to the "Low Ambient Temperature Air Source Heat Pump Unit Energy Efficiency Limit Value and Energy Efficiency Grade", the division standard of frost control demand evaluation index of air source heat pump is the average equivalent temperature drop ΔT of conventional air source heat pump unit in heating season of the city a The average equivalent temperature drop ΔT of conventional air source heat pump is abbreviated as conventional air source heat pump temperature drop ΔT a The frost control energy efficiency is reached within 6℃; (2) Determine whether there is a need for frost suppression in different regions; according to the hourly meteorological data of the typical meteorological year, calculate the average ΔT of the conventional air source heat pump in the heating season of the corresponding region a When the calculation result is greater than 6℃, it is determined that the region needs to select the frost suppression type air source heat pump; the constitutive configuration parameter CICO corresponding to the conventional air source heat pump is 6; (3) dividing threshold range of frost control demand; when 6 < ΔT a ≤ 8, selecting frost control air source heat pump with CICO = 8, when 8 < ΔT a ≤ 10, selecting frost control air source heat pump with CICO = 10, when 10 < ΔT a ≤ 12, selecting frost control air source heat pump with CICO = 12; (4) calculating the frost suppression effect of the selected corresponding frost suppression type air source heat pump in step (3); according to the selected frost suppression type air source heat pump CICO, calculating the average frost suppression type air source heat pump heating season defrosting equivalent temperature drop, i.e. the frost suppression type air source heat pump defrosting equivalent temperature drop ΔT under the CICO a ` (5) Verify whether the defrosting air source heat pump selected in step (3) meets the defrosting energy efficiency requirement. If it does not meet the requirement, the average defrosting equivalent temperature drop ΔT during the heating season is not met. a If the temperature is ≤6℃, return to step (3) and reselect the air source heat pump CICO; (6) Until the corresponding region meets the defrosting energy efficiency, then output the CICO of the air source heat pump selected for the corresponding region, which is the design and selection of the defrosting air source heat pump. In the above step, the equivalent temperature drop ΔT of defrosting of the conventional air source heat pump a is calculated by the formula (5) as follows: The equivalent temperature drop ΔT of defrosting in an air-source heat pump with defrosting function is as follows: a The formula for calculating ` is shown in (10):

2. The design and selection method for a frost-suppressing air source heat pump applicable to different regions as described in claim 1, characterized in that, The ΔT corresponding to the above steps a and ΔT a The determination of ` is carried out using the following steps: Under non-frost conditions, when the outdoor ambient temperature T a Below the nominal operating ambient temperature T an At the same time, the heating capacity of a conventional air source heat pump also decreases to Q as the outdoor temperature decreases. h1 The heating capacity is lower than the nominal operating condition Q. hn According to measured data, conventional air source heat pumps operate at an ambient temperature of T... a Heating capacity Q during frost-free operation h1 It can be calculated according to formula (1): With a constant ambient temperature, as the relative humidity (RH) increases, the performance of a conventional air source heat pump is affected by defrosting when entering frosting conditions. The heating capacity of the conventional air source heat pump decreases to Q. h2 This part of the performance loss ΔQ RH (△Q RH =Q h1 -Q h2 This is caused by the influence of relative humidity. According to measured data, conventional air source heat pumps operate at an ambient temperature of T... a The heating capacity Q during operation under frosting conditions with a relative humidity of RH h2 The formula for calculation is as follows (2): Q h2 =[0.311T a +0.043T a 2 +0.005T a 3 -(0.783-1.072×10 -4 T a 3 )RH 0.846 -1.647]×Q hn (2) The unit performance loss ΔQ caused by defrosting RH The loss is calculated based on the outdoor ambient temperature, as shown in formula (3): Performance loss ΔQ caused by defrosting process RH The difference between the unit's performance under frost-free and frost-covered conditions when the outdoor ambient temperature remains constant can be calculated using formula (4): △Q RH =Q h1 -Q h2 (4) Finally, the equivalent temperature drop ΔT for defrosting of a conventional air source heat pump can be obtained. a The calculation formula is shown in (5): A higher constitutive parameter CICO for an air source heat pump indicates stronger defrosting capability, less performance loss due to defrosting under the same operating conditions, and a lower equivalent temperature drop ΔT during defrosting. a The smaller; Under frosting conditions, the defrosting air source heat pump exhibits less heating capacity reduction compared to the conventional air source heat pump. The defrosting loss coefficient for the conventional air source heat pump is ε1, while that for the defrosting unit is ε2. Through mathematical analysis, the relationship between these two loss coefficients is as follows: ε2=ε1×β (6) In the formula: β is the correction factor for frost loss in air source heat pumps; Under the standard frosting condition of 2 / 1℃, the performance of six air source heat pumps with different constitutive configuration parameters CICO was tested. By analyzing the frosting loss of each heating cycle, the relationship between the frosting loss coefficients of air source heat pumps with different CICOs was obtained. Finally, the relationship between the frosting loss correction coefficient and CICO was obtained by nonlinear regression fitting, as shown in equation (7). β=-0.376×ln(CICO)+1.664 (7) Finally, substituting β into the performance model of a conventional air source heat pump under frost conditions, we can obtain the results for the anti-frost air source heat pump with constitutive parameters CICO and ambient temperature T. a The heating capacity Q during operation under frosting conditions with a relative humidity of RH h The formula that can be calculated is as shown in (8): Performance loss ΔQ caused by defrosting process RH The difference between the unit's performance under frost-free and frost-covered conditions when the outdoor ambient temperature remains constant can be calculated using formula (9): △Q RH ′=Q h1 -Q h (9) The equivalent temperature drop ΔT of defrosting in a defrosting air source heat pump can be obtained. a The formula for calculating ` is shown in (10):

Images