Thermal performance of a lightweight building with phase change material under a humid subtropical climate

The use of phase change materials(PCMs)in building enclosures is an efficient way to reduce the heat gain and/or loss in summer and winter.It was evident that the thermal performance of buildings with PCMs was affected by the outdoor air temperature significantly.However,the influence of humidity,which was serious in the humid subtropical climate was unclear.To explore the effect of PCMs under a humid subtropical climate,the thermal performance of a lightweight building outfitted with PCMs with a melting temperature of 25°C was investigated.The actual outdoor air temperature with a humidity of 40-90 RH%and wind velocity of 2-6 m/s blowing from the east,west,south,and north was assumed for the performance assessment.A simulated model was developed using EnergyPlus and verified against experimental data.The energy savings by using PCMs was reduced from 3.9%to 2.6%when the outdoor humidity increased from 40 to 90 RH%in summer.However,the savings was not obvious in winter.Annual energy savings decreased from 1.64%to 1.32%with humidity increasing from 40 to 90 RH%.For annual condition,the average energy savings was reduced from 1.43%to 0.92%when the wind speed increased from 2 m/s to 6 m/s.From an economic point of view,the investment payback period was less than 10 years when the PCM price was lower than 18.0 Yuan/kg.

Deflection test and modal analysis of lightweight timber floors

In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors,and strengthen the research on the coupling performance of the lightweight timber floors vibration characteristics and the building comfort,this article discusses the floor of a two-story prefabricated lightweight timber building demonstration house.In this paper,the floor structure of a two-story light-weight wooden house has been carried out on structural calculation modal and experimental modal,static uniform load and concentrated load deflection value testing.The evaluation of the deflection value of the floor structure,the mode shape,the coupling of the fundamental frequency mode parameters,and the vibration comfort were also studied.The results show that the fundamental frequency simulation value,one-way modal test value and two-way modal test value of the floor structure all meet the requirements of BS-6472(BS6472-1:2008).That is,the floor structure is not lower than 8 Hz design requirements,and meets the frequency of BS-6472(BS6472-1:2008).The weighted root mean square acceleration is lower than the requirement of 0.45 m/s^(2);the first three natural frequencies of the floor structure calculated by the finite element simulation are 16.413,31.847 and 48.921 Hz,and the fundamental frequency mode is the bending vibration in the length and width directions.The second order is the bending mode in the length direction,and the third order is the bending mode in the width direction.The fundamental frequency of the two-way modal test of the floor structure is the first-order bending mode in the X direction;and the second-order natural frequency is the second-order bending vibration shape in the X direction.when the uniform load is mainly the weight of floor own,the simulated maximum deflection value is 1.0658 mm;the simulation is performed according to the standard value of 0.566 kN/m for the uniform load of the floor design,and the simulation is the largest.The maximum deflection value of the simulated floor is 1.47383 mm at its midpoint,which meets the requirements of National Building Code of Canada-2015(NBCC).The maximum deflection limit of the light wood structure floor system is lower than 3 m and the maximum deflection limit is 2 mm;the six deflection value test lines simulated under a concentrated load of 1 kN all present a parabolic distribution and are symmetrical.The above results has engineering application value for promoting the research on the vibration characteristics of the fabricated lightweight timber floors structure and its optimization design.