The Testing Equipment to Study Heat Transfer through a Frame-Panel Enclosure Structure Fragment

Thermal properties of the panel - frame enclosure structures used for construction purposes in the city of Tyumen have been studied. The effect of filtration on the change in the thermal flow rate has been revealed.


Introduction
Panel-frame enclosure structures are widely used in present -day construction. Thermal losses in such products mainly depend on the air and/or steam filtration speed rate through insulation layer [1,2,3].
However, existing methods of thermotechnical calculations do not take into account this fact [4,5,6]. Nevertheless, for energy saving it is important to estimate the heat amount transported through the enclosure structure depending on filtrating degree (mass rate of gas flow). In turn, it is evident that the filtering degree will depend on the pressure difference in the layered construction, which is the frame-panel enclosure structure. Filtrating degree has become especially important after the new insulating layers with selectivity in gastransmission were invented. Experimental study approach here seems preferable, as it allows to evaluate the thermophysical properties of heat and mass transfer and mathematical model adequacy of the process under study.
It became possible to obtain the temperature distribution on the surface, as well as the actual heat flux density passing through the test structure at various differential pressures that are generated by various modes of built-in fans by using the presented automated research tool set.

The objects and methods of study
The aim of this study was to determine some thermophysical properties on the enclosure structure surfaces, such as temperature fields, surface density of heat flow, heat transfer dynamics and its dependence on the mass transfer degree through the layered structure.
The testing equipment was climate chamber heat-cold-moisture REOCAM TCM -1000, allowing to use objects in the temperature range -60 ÷ 100°C and relative humidity 20 ÷ 98% in the programmable mode. The main technical specifications are illustrated in Tab. 1. The fragment of the enclosure structure under analysis has a layered construction with the frame (see Figure 1    Testing procedure: 1. Thermoelectric sensors (TXK 0006) were attached to internal and external surfaces of the enclosure structure under testing by KPT heat-conducting paste -8. The sensors were connected to the IT-2 calculator. Temperature sensors placement is shown in fig. 3, 4, 7, 8.
The thermoelectric sensor No. 15 was attached between the external layer of gypsumchip board and slag wool, and the sensor No. 16 was attached between an inside layer of gypsum-chip board and slag wool to measure the insulation surface temperature both outside, and inside the enclosure structure.
Such geometrical position of sensors and measuring instruments is caused by simultaneous indicating on as large area as possible. Stiffening ribs placement has heat conductivity coefficient other than insulation conductivity coefficient. Specifications of the TXK 0006 thermoelectric sensors and the IT-2 calculator are given in table 3, 4.
Measuring instruments. Temperature and heat conductivity sensors (multichannel IT-2) consist of an IT-2 block and a set of connection box (compensation devices) UK-4 (1 piece per each of 16 canals). IT-2 are connected to the computer via the RS-232 interface. Each UK-4 contains the integrated temperature sensor of the thermocouple cold ends. Temperature multichannel IT-2 calculators take temperature sensors readings of the thermocouple cold ends on each of channels and transfer received data to the computer. The computer defines values of surface density of a thermal flow (q) or temperature (t) on the obtained data if necessary.
The received values are displayed on the computer in the form of voltage value (U), q or t. Temperature-cycle test is conducted. During each temperature-cycle test the IT-2 block tests all channels and transfers data to the computer. Calculators can test continuously ie temperature-cycle tests are conducted one by one, or they can conduct the required amount of temperature-cycle test. Calculators also conduct temperature-cycle tests with a programmable delay between cycles from 1 second till 60 min.    1. The sample of a enclosure structure under testing was attached to a working chamber by ropes.
2. The mode (cycle) of the camera operation was set. The schedule of the camera operation is given in fig. 9. 3. Gas filtration level through a layered construction was set by method of excess pressure or discharge from outer side.
4. The fragment under testing was exposed continuously to three cycles. Typical thermograms of a cycle are shown in fig. 10; surface densities of a thermal flow and temperature are given in fig. 11. 5. Test results were mathematically processed in the normal extension using Student's test.

Conclusions
The presented experimental complex allows to carry out a wide range of heat-physical properties studies necessary to assess the enclosure structure heat saving efficiency.
The testing equipment is completely computer-aided which allows to conduct testing continuously saving results. Statistical processing is also computer-aided which increases the studies efficiency and excludes mistakes.
It is now possible to carry out a comparison of experimental study and simulation (in the measurement points) results in real time. The testing equipment is universal, as it allows to study the heat and mass transfer processes in multilayer enclosure structures without readjustment (or with small readjustment).
The automated research's stand, which was described in the article, allows to make realtime study of the interrelated processes of heat and mass transfer with air filtration, the level of measuring's equipment automation allows us to simulate the impact of external factors such as temperature, barometric pressure difference and to conduct a statistical analysis of the measured data.
New experimental information about the interrelation of distribution of temperature, pressure differential, heat flux density of studied construction of the exterior wall panel in a non-stationary thermal and mass transfer processes occurring in the building materials were received. The results of our research are applicable in the validation of computational models by quantitative comparison of the calculated temperatures distribution, pressure differences and heat flux density.