Name: study on the moisture absorption and desorption rate of bamboo scrimber in a hot-humid climatic wind tunnel
Uploaded: 2018-03-09T13:54:44
Description: The absorption and desorption rate Uab is an important indicator to evaluate the hygric performance of hygroscopic building materials. However, standard ...

The research was funded by The State Key Laboratory of Subtropical Building Science Project: 2017KC22 and The State Scholarship Fund by the Chinese Scholarship Council: 201506150017.
The experiment was carried out with the Hot-Humid Climatic Wind Tunnel (HHCWT), which was developed by the Building Energy Conservation Research Center of South China University of Technology.

1. Specimens Treatment
<ol>
	<li>Specimens preparation
	<ol>
		<li>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).</li>
		<li>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...

<ol>
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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&#39;s treatment, which in turn included the specimen&#39;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...

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 environments1,2. 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.
The moisture absorption and desorption rate Uad are an important indicator characterizing the hygric transport performance, and also closely affect the thermal performance of certain building materials, especially for those hygroscopic materials such as bamboo and timber. Normally, the Uad value is measured by static standard methods in a laboratory environment, with constant ambient air temperature T and relative humidity RH (e.g., T = 23 &#176;C, RH = 50%)3. However, the constant indoor testing conditions are very different from the practical application in an outdoor environment, where the meteorological conditions are more complex. The effect of solar radiation on the heat and moisture transfer cannot be ignored4,5. Other studies have investigated the dynamic performance by establishing dynamic models and transfer functions6,7 andshow different characteristics compared to the static standard tests8.
To test the material objects in real outdoor climate conditions is a more persuasive method to evaluate the targeted performance. However, outdoor climate conditions do not reappear, making the experiments difficult to standardize, let alone when done by different operators at different periods. For solving the above challenges, we studied reproducible meteorological conditions and developed them with a climate wind tunnel. A wind tunnel is a comprehensive concept to create different simulated conditions (e.g., wind resistance testing, evaporative cooling, or a microclimate on building envelope) to examine certain performances of the research objects9,10,11,12.
For this study, the HHCWT was created with a motivation to reproduce the outdoor climate conditions for examining the hygrothermal performance of building materials and building components closer to the practical application conditions13,14. The HHCWT consists of 18 elements: a protection room (Figure 1.1) with an air conditioner, a heater, a humidifier, a dehumidifier (Figure 1.12 - 1.15), a wind tunnel (Figure 1.2) with an entrance region, a stilling region, a test region, an auxiliary region, a diffusion region and a fan region in the order (Figure 1.5 - 1.10), a solar radiation chamber (Figure 1.11) overhead and an air conditioning chamber (Figure 1.16) below, the specimen slot (Figure 1.4) with a balance (Figure 1.17) on the boundary of the wind tunnel and the air conditioning chamber (Figure 1.3), and the operating condition control and data collection system (Figure 1.18) outside the protection room. An operating condition control and data collection system were set outside the protection room for the input and output control of the whole system. The climatic wind tunnel enabled the complete control of climate conditions, therefore realizing the repeatability and standardization of the climate-related experiment (Figure 1).
In this study, a dynamic absorption and desorption pair-test was carried out for bamboo scrimber and hardwood specimens. The HHCWT was used to create complete climate conditions, including the solar radiation, air temperature, relative humidity, and wind speed of a TMD (Typical Meteorological Day) of Guangzhou, a typical subtropical city located in the south of China. The obtained values were compared with the results from the static standard method to show the progress of this experimental method.
Since factors such as bulk density, open porosity, and surface treatment had an impact on the hygric properties of the products15,16, typical samples were selected from the company that owned the core patent (Table 2).

<table border="0" cellpadding="0" cellspacing="0" width="716">
	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:179px;">bamboo scrimber sample</td>
			<td style="width:179px;">Dasso Industrial Group Co. Ltd. Hangzhou, China</td>
			<td style="width:179px;">-</td>
			<td style="width:179px;">made of Phyllostachys Pubescens, mainly used for outdoor flooring</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:179px;">Hardwood sample</td>
			<td style="width:179px;">Shan Shang industry, Shanghai, China</td>
			<td style="width:179px;">-</td>
			<td style="width:179px;">made of Intsia.spp, Caesalpiniaceae, mainly used for outdoor flooring</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:179px;">Petroleum jelly</td>
			<td style="width:179px;">Guangzhou Suixin Chemical Co., Ltd.</td>
			<td style="width:179px;">-</td>
			<td style="width:179px;">White Vaseline</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:179px;">Balance</td>
			<td style="width:179px;">Shimadzu</td>
			<td style="width:179px;">UX 6200H</td>
			<td style="width:179px;">Range 0.5-6200 g, accuracy 0.01g</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:179px;">Vacuum pump</td>
			<td style="width:179px;">Dongguan Fopump Vacuum Equipment Co., Ltd., Dongguan, China</td>
			<td style="width:179px;">2X-8</td>
			<td style="width:179px;">Sliding vane rotary vacuum pump, extreme pressure 600Pa, speed 8L/s</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:179px;">HHCWT: Hot-Humid Climatic Wind Tunnel, including control systems for:</td>
			<td style="width:179px;">the Building Energy Conservation Research Center of South China University of Technology</td>
			<td style="width:179px;">-</td>
			<td style="width:179px;">The HHCWT consists of 18 elements (table 3)</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:179px;">Software attached to the HHCWT operating condition control and data collection system</td>
			<td style="width:179px;">the Building Energy Conservation Research Center of South China University of Technology</td>
			<td style="width:179px;">-</td>
			<td style="width:179px;">Created by visual programming language Visual Basic</td>
		</tr>
	</tbody>
</table>

study on the moisture absorption and desorption rate of bamboo scrimber in a hot-humid climatic wind tunnel

The absorption and desorption rate Uab 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 Uab mean value and maximum value were, respectively, 64.35% and 66.02%. The maximum absorption rate Ua.max and desorption rate Ud.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.

The recorded data of the last 48 h from the whole 72 h were selected and analyzed (Figure 2, Table 5).
The dynamic test in the wind tunnel was performed and the results showed that the bamboo scrimber (BFB) had a lower Uad value than the reference hardwood (HW). Compared to HW, BFB showed a more stable hygric performance. The Uab mean value Uab.mean ...

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.

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

The absorption and desorption rate Uab is an important indicator to evaluate the hygric performance of hygroscopic building materials. However, standard ...