determined by both The amount of heat transferred is the heat transfer from the air and the radiation from the glass from Eden Hamilton's blog

Because of its high vacuity, VIG has provided the world with excellent heat insulation, condensation resistance, and sound insulation.

Insulation against the heat

Regarding VIG structure, the edge is soldered, and the center is separated by supports to form a vacuum chamber. As a result of the above structure, the heat transfer coefficient in the central area of the VIG is far less than that in its edge, and when considering practice in the real world, the heat transfer in the edge is associated with the window frames. Consequently, the U value in the central area of the glass is only measured for the purpose of parameter comparability and not for any other reason.

When the VIG is in the center of the room, heat transfer is carried out by radiation, support contact, and residual gas. According to Jianzheng Tang's The Vacuum Insulated Glazing Heat Transfer Coefficient and the Calculation of the Condensation Temperature, when the vacuity is less than 0.1 Pa, the heat transfer from residual gas can be ignored, and the heat transfer coefficient of VIG is determined by the emissivity of the glass as shown in Formula 1.

Heat transfer through insulated glass (IGU) is determined by both air heat transfer and glass radiation, with air heat transfer taking precedence over glass radiation in the majority of cases. The heat transfer coefficient of insulated display cabinet door is significantly higher than the coefficient of VIG from the original glass with the same emissivity on which it is based.

Note: R1 represents the thermal resistance of the inside glass; R2 represents the thermal resistance of the outside glass; Rradiation represents the thermal resistance of the radiation; Rsupport represents the thermal resistance of the support; Rair represents the thermal resistance of the gas residual; Rvacuum represents the thermal resistance of the VIG; Cvacuum represents the conductivity of the VIG.

 Anti-condensation measures

The anti-condensation performance is divided into two categories:

Table 3 shows a comparison of the condensation performance of insulated glass and VIG, with the result being that VIG has a better anticondensation performance than insulated glass. To start condensing the VIG under the conditions of 25 degrees Celsius inside and 75% relative humidity, the temperature outside must be at least -69.5 degrees Celsius; however, with insulated glass, the critical temperature is only required to be reached at -4 degrees Celsius.

As shown in Figure 4, the acoustic insulation performance is relatively poor in the frequency range of 160-6300 Hz for frequencies less than 500 Hz. The reason for this is that the low frequency is more likely to cause the quisure insulated glass to vibrate, and the sound energy is transferred from one side to the other side through the pillars.

When operating in the frequency range of 500Hz to 3150Hz, the sound insulation properties of glass are relatively good. In this case, the maximum is 42. 5dB at 1250Hz, and the minimum is 35dB. This means that the sound insulation performance of VIG is significantly better than that of laminated glass and insulated glass. For example, the sound transmission loss of 5+ 0.3V +5 VIG is only 26dB, while that of 5+9A+5 insulated glass is only 32dB; and that of 5+0.76p +5 laminated glass is only 32dB.

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