Study on the Moisture Absorption and Desorption Rate of Bamboo Scrimber in a Hot-Humid Climatic Wind Tunnel

Summary

Here, we present a protocol to measure the moisture absorption and desorption rate of bamboo scrimber in an outdoor environment for a dynamic hot-humid climate wind tunnel test with complete meteorological conditions for 72 h.

Abstract

The absorption and desorption rate U_ab is an important indicator to evaluate the hygric performance of hygroscopic building materials. However, standard methods to obtain this value are normally carried out in a static indoor environment, which cannot represent a dynamic outdoor environment. This protocol presents a Hot-Humid Climate Wind Tunnel (HHCWT) method to examine the hygric behavior of bamboo scrimber (BFB) in outdoor conditions, with the hourly solar radiation, air temperature, relative humidity, and constant wind speed of a typical summer day in the south of China. The complete meteorological parameters were repeated for 72 h, of which the last 48 h were selected for analysis. By comparison with the hardwood specimen (HW) in this test, BFB showed a more stable hygric performance. The BFB to HW ratio of the U_ab mean value and maximum value were, respectively, 64.35% and 66.02%. The maximum absorption rate U_a.max and desorption rate U_d.max from the dynamic test were correspondingly 2.91E^-05 kg/(m²/s) and 4.45E^-05 kg/(m²/s), far larger than the results of 7.74E^-07 - 12.58E^-07 kg/(m²/s) from the static test. The significant difference in magnitude shows the necessity of a dynamic evaluation approach that can take more practical climate conditions into consideration. The HHCWT enables the reproducibility and standardization of climate-related experiments for building materials by creating climate conditions with complete meteorological parameters.

Introduction

Bamboo scrimber is considered to be an ideal product to achieve a high value-added utilization of the widely distributed bamboo forest resources, by decomposing raw bamboo and recombining it into bamboo panels that could be applied as outdoor flooring or a building facade. There already are studies on the hygrothermal properties of bamboo scrimber with static standard methods carried out in indoor environments^1,2. However, the performance in more practical outdoor conditions needs further investigation. The hygric properties of bamboo scrimber obtained in our prior study are shown in Table 1.<....

Protocol

1. Specimens Treatment

1. Specimens preparation
   1. Select the material: for the bamboo (BFB), a bamboo scrimber panel made of Moso (Phyllostachys Pubescens); for the timber (HW), a hardwood panel made of Intsia spp. (Caesalpiniaceae).
   2. Ask the bamboo and wood factories to cut the specimens to a size of 30 x 30 cm (side length), while keeping the original thickness of 28 mm.
      Note: The normal size of the bamboo panels used is 122 x 244 cm (width x lengt.......

Discussion

The protocol presented a Hot-Humid Climatic Wind Tunnel (HHCWT) test method to measure the moisture absorption and desorption rate of bamboo scrimber. The critical steps included the specimen's treatment, which in turn included the specimen's preparation, vacuum saturation, and bottom and side sealing; the wind tunnel operation, which in turn included the equipment arrangement, wind tunnel preheating, specimens installation, and data recording; the post-operation including drying the specimen; the data processing.......

Materials

Name	Company	Catalog Number	Comments
bamboo scrimber sample	Dasso Industrial Group Co. Ltd. Hangzhou, China	-	made of Phyllostachys Pubescens, mainly used for outdoor flooring
Hardwood sample	Shan Shang industry, Shanghai, China	-	made of Intsia.spp, Caesalpiniaceae, mainly used for outdoor flooring
Petroleum jelly	Guangzhou Suixin Chemical Co., Ltd.	-	White Vaseline
Balance	Shimadzu	UX 6200H	Range 0.5-6200 g, accuracy 0.01g
Vacuum pump	Dongguan Fopump Vacuum Equipment Co., Ltd., Dongguan, China	2X-8	Sliding vane rotary vacuum pump, extreme pressure 600Pa, speed 8L/s
HHCWT: Hot-Humid Climatic Wind Tunnel, including control systems for:	the Building Energy Conservation Research Center of South China University of Technology	-	The HHCWT consists of 18 elements (table 3)
Software attached to the HHCWT operating condition control and data collection system	the Building Energy Conservation Research Center of South China University of Technology	-	Created by visual programming language Visual Basic