A dynamic test method for thermal performance of prefabricated ceiling radiation panels

Abstract

The present invention belongs to the field of HVAC technology, and discloses a dynamic test method for the thermal performance of a prefabricated ceiling radiation panel. The thermal resistance, thermal capacity, and thermal response time of the radiation panel are obtained through thermal performance experiments to measure the thermal performance of the prefabricated ceiling radiation panel, and the problems of inconsistent environmental benchmarks and test results not being suitable for dynamic operation and regulation of the system in the existing steady-state test methods are solved. The thermal resistance, thermal capacity, and thermal response time obtained by the dynamic test method of the present invention can accurately evaluate the dynamic thermal response characteristics of the ceiling radiation panel, and the energy conservation equation obtained in the dynamic heat exchange process can be used for precise dynamic regulation of the prefabricated ceiling radiation panel, which is of great significance for achieving system optimization and regulation.

Description

Technical Field

[0001] The invention belongs to the technical field of heating, ventilation and air conditioning, and relates to a dynamic testing method for thermal performance of a prefabricated suspended ceiling radiation panel. Background Art

[0002] The thermal performance of prefabricated ceiling radiant panels is of great significance for their design selection and operation control. Although the relevant standards on the thermal performance of radiant panels, such as JGT 403, JGT 409, and JB / T 12842, are different in test benchmarks and test ranges, the test experiments use the internal heat source method or the external heat source method to balance the cooling and heating of the ceiling radiant panels, and the test principle uses a steady-state test method to test the cooling and heating, surface temperature, and reverse heat transfer loss of the ceiling radiant panels by giving parameters such as water supply temperature and flow. Then, these standards describe the thermal performance of ceiling radiant panels based on the surface temperature or excess temperature of the ceiling radiant panels (the difference between the reference point temperature and the average water temperature). For example, JGT 403, JGT 409, and JB / T 12842 all describe the thermal performance of ceiling radiant panels by giving the relationship between the cooling and heating capacity and the excess temperature. However, the surface temperature of the ceiling radiant panels is the result of the combined effect of various parameters (water side parameters, characteristics of the radiation device itself, indoor environment, etc.). The single relationship between the surface temperature or excess temperature of the ceiling radiant panels and the cooling and heating capacity has the problem of inconsistent environmental benchmarks, resulting in a large error between the cooling and heating capacity of the actual room radiant panels and the experimental test results. In addition, the results obtained by the steady-state test method are only applicable to the calculation of the cooling and heating capacity of the radiant cooling and heating system after it is stabilized, and are not suitable for dynamic operation and regulation of the system. Summary of the invention

[0003] The present invention provides a dynamic testing method for the thermal performance of a prefabricated ceiling radiation panel. The thermal performance of the prefabricated ceiling radiation panel is measured by obtaining parameters such as thermal resistance, thermal capacity, and thermal response time of the radiation panel through a thermal performance experiment, thereby solving the problems of inconsistent environmental benchmarks and test results being unsuitable for dynamic operation and regulation of the system in existing steady-state testing methods.

[0004] The technical solution of the present invention is as follows:

[0005] The concept of thermal resistance R of the ceiling radiation panel (the heat transfer resistance from the cold and hot media in the ceiling radiation panel to the surface of the ceiling radiation panel) is used to simplify the multi-dimensional heat transfer problem of the ceiling radiation panel. w The average surface temperature of the ceiling radiation panel T s The heat transfer per unit area q1 of the cold and hot media to the surface of the ceiling radiation panel can be described as:

[0006]

[0007] The heat exchange between the ceiling radiation panel surface and the room is mainly achieved through convection heat exchange and radiation heat exchange. The convection radiation comprehensive heat transfer coefficient h z (Cooling takes 11W / (m 2 . K), heating takes 7W / (m 2 . K)), average surface temperature of ceiling radiation panel T s and reference point air temperature T a The heat q2 transferred from the ceiling radiation panel surface to the room can be described as:

[0008] q2=h z (T a -T s ) (2)

[0009] The ceiling radiation panel will also have its own heat storage when the temperature rises and falls. The concept of heat capacity per unit area C is used to describe the dynamic heat transfer process of the ceiling radiation panel. The energy conservation equation is:

[0010]

[0011] When the non-steady-state term on the left side of the energy conservation equation is 0 (steady-state heat transfer), it can be concluded that the surface temperature of the ceiling radiation panel after stabilization is T e :

[0012]

[0013] Using the stabilized ceiling radiation panel surface temperature T e And the initial temperature T0 of the ceiling radiation panel surface, we can get the average surface temperature of the ceiling radiation panel to satisfy:

[0014]

[0015] The time constant refers to the time when the surface temperature change of the ceiling radiation panel reaches 63.2% of the total change, expressed as τ, as shown in the following formula:

[0016]

[0017] When the surface temperature of the ceiling radiation panel reaches the time constant τ, the surface of the ceiling radiation panel is still in a temperature rise state, and the surface temperature of the ceiling radiation panel reaches the thermal response time τ 95 After that, the temperature is basically in a stable state, that is, the thermal response time is closer to the stabilization time. Therefore, the thermal response time τ 95 It can more intuitively reflect the energy of prefabricated ceiling radiation panels. 95 The concept can be obtained:

[0018]

[0019] According to the concept of thermal response time, the equation for the change of the surface temperature of the ceiling radiation panel can be simplified as:

[0020]

[0021] Use technical measures (usually closed chambers) to control the air temperature T at the reference point in the room where the prefabricated ceiling radiant panels are installed. a And the inlet and outlet water temperature of the ceiling radiation panel is stable T w Then, the measuring points are arranged reasonably to continuously collect the surface temperature of the ceiling radiation panel. The average surface temperature T of the ceiling radiation panel is obtained by the average value of each surface temperature measuring point of the ceiling radiation panel. s The obtained data of the average surface temperature of the ceiling radiation panel are fitted according to the surface temperature variation equation of the ceiling radiation panel, and (T0-T e ), τ 95 、T e The values ​​of the coefficients of the equation are:

[0022] The thermal resistance R of the ceiling radiation panel is:

[0023]

[0024] The heat capacity C (heat capacity per unit area) of the ceiling radiation panel is:

[0025]

[0026] Beneficial effects of the present invention:

[0027] 1. The present invention proposes to use the thermal resistance of the radiation panel to accurately and quickly calculate the heat transfer of the radiation panel. Compared with the relationship between the surface temperature or excess temperature and the cooling and heating supply adopted in the traditional steady-state test method, it can avoid the error caused by the difference between the experimental test environment and the actual room environment, and at the same time can reduce the number and time of experimental tests.

[0028] 2. The thermal resistance, thermal capacity and thermal response time obtained by the dynamic testing method of the present invention can accurately evaluate the dynamic thermal response characteristics of the ceiling radiation panel, and the energy conservation equation of the dynamic heat exchange process can be used for the precise dynamic regulation of the prefabricated ceiling radiation panel, which is of great significance for achieving system optimization and regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of the arrangement of air temperature measurement points of the present invention, wherein a is the test sample, b is the c b is the reference point air temperature measurement point for radiant cooling, h It is the reference air temperature measuring point for radiant heating, and c, d, e, and f are other air temperature measuring points.

[0030] Figure 2 is a schematic diagram of the surface temperature measurement points of the ceiling radiation panel of the present invention, wherein ①~ Temperature measuring points arranged on the surface of ceiling radiation panels. Temperature measuring points on the surface of ceiling radiation panels are generally arranged in pairs (in principle, there should be no less than 5 pairs, half of which should be evenly arranged on the heating and cooling pipes along the flow of cold and hot media, and the other half should be evenly arranged in the middle of the heating and cooling pipes along the flow of cold and hot media), evenly distributed over the entire surface of the ceiling radiation panels. For irregular surfaces, large areas, and surfaces with uneven temperatures, the number of measuring points should be appropriately increased.

[0031] Figure 3 It is the fitting curve of the average surface temperature of the ceiling radiation panel. DETAILED DESCRIPTION

[0032] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0033] The basic requirements for the experimental test system are as follows:

[0034] The experimental system, calibration of test instruments and test preparation for the dynamic test method of thermal performance shall be carried out in accordance with the provisions of the current industry standard JGT 403 "Thermal Performance Test Method for Radiant Cooling and Heating Devices".

[0035] The test sample should meet the requirements of the current industry standard JGT 403 "Thermal Performance Test Method of Radiant Cooling and Heating Devices". The test and installation should meet the following requirements: (1) The side length of the test sample should be 1.0 to 3.4 m and it should be laid in the center of the closed chamber; (2) The cooling capacity of the test sample under standard working conditions should not be less than 120 W, the heating capacity under standard working conditions should not be less than 200 W, and the cooling (heating) capacity for the cubic meter test chamber volume should not be greater than 87 W; (3) During the test, the test sample should be installed on the bracket according to its use status. Insulating materials should be installed around the test sample, and the thermal insulation resistance should not be less than 1.0 (m 2 ·K) / W.

[0036] Reference point air temperature measurement point Figure 1 As shown, the reference point temperature (b c , b h ) The expanded uncertainty of the measurement system (k=2) should not be greater than 0.1℃. The expanded uncertainty of the measurement system (k=2) of other temperature measuring points (c, d, e, f) should not be greater than 0.2℃. All air temperature measuring points should be shielded against thermal radiation.

[0037] The specific test requirements for the inlet and outlet water temperatures of suspended ceiling radiation panels are as follows: (1) The inlet and outlet water temperatures should be measured at the connection point between the test sample and the water system. If it is not possible to measure at the connection point, the distance between the temperature measurement point and the connection point between the test sample and the water system should not be greater than 0.3m, and the pipe section should be strictly insulated, and the insulation layer should extend more than 0.3m beyond the temperature measurement point; (2) The temperature detected by the temperature sensor should be representative of the average temperature of the water flow; (3) The expanded uncertainty of the temperature measurement system (k=2) should not be greater than 0.1°C; (4) The consistency of the inlet and outlet water temperature measurements should be ensured, and the expanded uncertainty of the temperature difference between the inlet water temperature and the outlet water temperature (k=2) should not be greater than 0.05°C.

[0038] The measurement points for the average surface temperature of the ceiling radiation panel are arranged as follows: Figure 2 The specific requirements are as follows: (1) The thermometer should be tightly attached to the surface of the radiator; (2) The average surface temperature of the ceiling radiation panel T s The arithmetic mean of the temperature at each measuring point should be taken; (3) The expanded uncertainty (k = 2) of the temperature measurement system for the surface temperature of the ceiling radiation panel should not be greater than 0.1°C.

[0039] The specific test steps are as follows:

[0040] (1) Experimental preparation and safety inspection.

[0041] (2) Hot and cold water is introduced into the ceiling radiation panels and the walls of the closed chamber to keep the surface temperature of the ceiling radiation panels and the reference point air temperature at 26°C (for cooling) or 20°C (for heating), and to maintain stability.

[0042] (3) Hot and cold water with constant temperature is introduced into the ceiling radiation panel, and the temperature of the hot and cold water in the wall of the closed chamber is adjusted by the temperature control device so that the air temperature at the reference point remains unchanged. The surface temperature measuring point of the ceiling radiation panel, the reference point air temperature and the water inlet and outlet measuring points of the ceiling radiation panel are dynamically collected. The collection time interval should not be less than 1 minute. At least 12 tests are performed at equal time intervals until the test system reaches a steady-state condition.

[0043] (4) Analyze whether the measured data meets the error requirements. If not, repeat steps (2) and (3).

[0044] (5) Figure 3 As shown, the temperature rise curve is fitted by using the average surface temperature of the ceiling radiation panel, the average surface temperature of the ceiling radiation panel is calculated according to the dynamically collected temperature data, and the temperature rise curve of the ceiling radiation panel surface is fitted by using the least square method.

[0045] (6) According to the temperature rise curve and calculation formula, the thermal resistance R, heat capacity C and thermal response time τ are obtained 95 .

[0046] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A dynamic test method for thermal performance of prefabricated ceiling radiation panels, characterized in that: The details are as follows: The heat transfer resistance from the cold and hot media in the ceiling radiation panel to the surface of the ceiling radiation panel is defined as the thermal resistance of the ceiling radiation panel. , using the thermal resistance of the ceiling radiation panel The multi-dimensional heat transfer problem of the ceiling radiation panel is simplified, and the average temperature of the cold and hot media is used. Average surface temperature of ceiling radiation panel The heat transfer per unit area of ​​the cold and hot media transferred to the ceiling radiation panel surface Described as: The heat exchange between the ceiling radiation panel surface and the room is mainly achieved through convection heat exchange and radiation heat exchange. The convection radiation comprehensive heat transfer coefficient is used. , Average surface temperature of ceiling radiation panel and reference point air temperature Transfer the heat from the ceiling radiant panel surface to the room Described as: The ceiling radiation panel will also have its own heat storage when the temperature rises and falls, using the heat capacity per unit area The energy conservation equation describing the dynamic heat transfer process of the ceiling radiation panel is: When the non-steady-state term on the left side of the energy conservation equation is 0, the surface temperature of the ceiling radiation panel after stabilization is obtained as follows: : Using the stabilized surface temperature of the ceiling radiation panel and the initial temperature of the ceiling radiation panel surface The average surface temperature of the ceiling radiation panel satisfies: The time constant refers to the time when the surface temperature change of the ceiling radiation panel reaches 63.2% of the total change. It is represented as shown in the following formula: When the surface temperature of the ceiling radiation panel reaches the time constant The surface of the rear ceiling radiation panel is still in a state of temperature rise, and the surface temperature of the ceiling radiation panel reaches the thermal response time After that, the temperature is basically in a stable state, that is, the thermal response time is closer to the stabilization time; therefore, the thermal response time More intuitively reflect the performance of prefabricated ceiling radiation panels and obtain: According to the thermal response time, the equation for the change of the surface temperature of the ceiling radiation panel is simplified to: in, Indicates time; Control of air temperature at a reference point in a room with prefabricated ceiling radiant panels using closed cells The inlet and outlet water temperatures of the ceiling radiation panels are stable Then, the measuring points are arranged reasonably to continuously collect the temperature of the surface of the ceiling radiation panel. The surface temperature measuring points of the ceiling radiation panel, the reference point air temperature and the water inlet and outlet measuring points of the ceiling radiation panel are dynamically collected. The collection time interval should not be less than 1 minute. At least 12 tests are performed at the same time interval until the test system reaches a steady-state condition. The average surface temperature of the ceiling radiation panel is obtained by the average value of each surface temperature measuring point of the ceiling radiation panel. ; The obtained data of the average surface temperature of the ceiling radiation panel are fitted according to the surface temperature variation equation of the ceiling radiation panel to obtain , , The values ​​of the coefficients of the equation are: Thermal resistance of ceiling radiant panels for: Heat capacity of ceiling radiant panels for: 。

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