Simulation of condensation problems in a roller-skating centre

A commercial roller-skating centre in southern Australia had condensation problems on both the roof and floor. The building is a typical warehouse-type structure with a high level of natural ventilation due to poor construction and permanently open vents. A computer model of the building, using the thermal simulation software TRNSYS, was calibrated from a sensitivity analysis of three key parameters, namely air exchange rate, roof surface heat transfer coefficient and deep ground temperature. The predicted times of condensation on the roof were compared with site observations. The time of year was predicted with acceptable accuracy, although earlier in the morning than had been observed. The effect of installing foil insulation in the roof was simulated. Under normal winter conditions, this modification was enough to stop the condensation. However, in unusually cold and humid conditions, condensation still occurred on both surfaces. This was overcome by heating the floor (15 W/m 2 ) for approximately eight hours. Subsequent modifications have demonstrated the value of the simulations.

Melamine–melem adduct phases: Investigating the thermal condensation of melamine

By studying the thermal condensation of melamine, we have identified three solid molecular adducts consisting of melamine C3N3(NH2)3 and melem C6N7(NH2)3 in differing molar ratios. We solved the crystal structure of 2 C3N3(NH2)3⋅C6N7(NH2)3 (1; C2/c; a=21.526(4), b=12.595(3), c=6.8483(14) Å; β=94.80(3)°; Z=4; V=1850.2(7) Å3), C3N3(NH2)3⋅C6N7(NH2)3 (2; Pcca; a=7.3280(2), b=7.4842(2), c=24.9167(8) Å; Z=4; V=1366.54(7) Å3), and C3N3(NH2)3⋅3 C6N7(NH2)3 (3; C2/c; a=14.370(3), b=25.809(5), c=8.1560(16) Å; β=94.62(3)°; Z=4; V=3015.0(10) Å3) by using single-crystal XRD. All syntheses were carried out in sealed glass ampoules starting from melamine. By variation of the reaction conditions in terms of temperature, pressure, and the presence of ammonia-binding metals (europium) we gained a detailed insight into the occurrence of the three adduct phases during the thermal condensation process of melamine leading to melem. A rational bulk synthesis allowed us to realize adduct phases as well as phase separation into melamine and melem under equilibrium conditions. A solid-state NMR spectroscopic investigation of adduct 1 was conducted.