热湿地区采用的辐射冷顶板加置换通风系统secret.doc

附录三：外文翻译 能源与建筑 36(2004年36期)1273-1280热湿地区采用的辐射冷顶板加置换通风系统Doosam Song a , Shinsuke Kato b,a 韩国，Suwon，Chun chun-dong 300号，Sungkyunkwan大学建筑工程学院,邮编：440-746, b 日本，东京，Meguro-ku Komaba 4-6-1号，东京大学工学院，邮编：153-8505, 收稿：2003年4月8日; 改稿：2003年7月18日摘要：这篇文章调查一个混合的冷却系统, 利用风驱动的置换通风和辐射冷却板。室内环境特性使用计算流体力学 (CFD) 模拟,结合辐射传热模拟，以及HVAC控制使得在房间中的人体模型的PMV值达到目标值。系统与一个节约能源的策略一起设计，这用一个垂直的温度梯度利用房间内分层的空气。被冷却的空气在房间的较下层稳定下来，当热湿空气经过过房间的上层区域的时候，排除出热量和室内产生的污染物。这一个策略被发现在日本的春天和秋天间的季节相当附合能源效率。甚至在热湿的户外情况之下, 与配有辐射冷却的混合系统会带来重要的节能，是可以与一个外加地板空调系统的混合系统相比较的。关键字:混合冷却系统; 自然通风; 辐射板冷却; CFD1. 介绍考虑自然通风是非常有效的能源策略，因为它利用自然力。在包括日本的亚洲的热湿区域中调整自然通风的户内环境中种传统方法。然而，在现代的建筑物，确定性、可信度和效率被首先考虑，自然通风的独立使用是不适当的。一个混合空调系统采用受约束的自然通风，或结合自然通风的机械的空调被考虑用以克服纯粹自然通风的缺点，而且有节约能源的效果。许多研究已经在欧洲和日本的自然通风制度和混合空调系统上被使用。在日本的个别混合冷却系统项目，结合自然通风的地板空调被广泛采用。但是许多研究已经发现辐射制冷在许多区域比传统的空调系统更为有效。在这研究，我们主张使用自然通风和辐射板冷却的混合冷却系统。它基于采用自然通风和辐射板冷却，对准目标根据置换通风引导户外的空气进入户内空间而且利用自然力尽可能达到更远的热条件。即使采用比较高的户外温度置换通风的方式冷却一个房间是不可能的，但户外的空气能仍然通过传入和经过房间的上层空间的途径，排除热和在室内产生污染物。在此同时, 在垂直热梯度的帮助下, 房间温度较低的部份可以由镶嵌在它里面的辐射板进一步冷却。这一个策略被认为在室内是高效率并能提供适当的热舒适。在这篇论文中，混合冷却系统用于描述室外的空气温度和相对湿度介于2160%和3070%之间的标准结果。2. 辐射冷却系统加自然通风的概念图1是在这个系统的研究概图。这一个冷却系统在房间的上部设置风口向室内提供新风进行自然通风并排除房间中被产生的热。除湿辐射地板安装在房间的下部用以控制室内的湿度并供冷。即使当户外的温度相对室内供冷较高，但是室内产生的热和污染物也能不在室内逗留占据空间，而随自然通风从房间上部通过风口排出室外，在房间的较低的部份中安装的辐射冷却板也只局部产生制冷效果。因此这种系统重视采用自然力调节的室内的环境的可能性, 但是取它在舒适度的水平下的最佳化用以维持户内的环境从而达到节约能源的目的。3. CFD 分析概述房间分析模型混合冷却系统即可以用于住宅业可以用于办公大楼。在这里，我们研究办公大楼。办公室设定在图3中，房间的长度是10.8m。被分析的区域设定在的办公室宽度3.6m的一半的地方 (1.8m), 形成一个对称的结构。混合冷却模型中户外的空气从窗户(0.5m *1.8m; 图 3左侧)进入房间上层流动的時候, 从另一侧(0.5m*1.8m; 图3右侧)排出, 与此同时辐射制冷正在工作。辐射冷板被设置在书桌前的隔板内, 而且在露点温度下就能工作。然而在地板下的空调系统混合的冷却系统的情况下，被冷却的空气来自地板的漫射器供应。人、照明、个人计算机, 太阳的得热, 及其他产生制冷负荷, 由自然通风来走，和辐射制冷或地板空调系统一起。人的模型安置在房间的中心作为热舒适感应器。4 . 结果4.1 . 流场区域不同的流场区域如图7所示。在案例1 (自然通风加辐射冷却系统)，由于室内空气(26.6)与室外空气(21)温度不同的考虑，负浮力效应对流动空气的影响显而易见。流动空气向下流动到窗口侧，与房间较低部分的室内空气相混合。虽然没有列在这里,风冷的辐射板向下流动到地上。例2 (自然通风空气流) 如案例1一样显示了同样的趋势。但是,空气与地下置换通风的空气相混合朝房间的较高的地方流动. 由于房间里的垂直温差, 室内产生了顺时针环流。在例3中,由于室内和室外空气的温差不大, 负浮力效应对流体空气的影响不是很明显. 对于冷顶板,电脑的热流上升,从图7（c)可以清楚看到. 这是因为任务区的平均气温下降所引起的. 但在4个例子中,由于垂直温差,室外空气下沉到地板表面. 4.2 . 温度分布四个例子的温度分布如图8所示。例一中室内平均温度为26.6，略高于案例2，24.4 然而，垂直温差不大,在约2度。在例2中，由于较低的风速( 0.8米/秒)，地板附近温度跌至近20度。结果，不同的房间垂直温度骤然下降了6，尤其是在房间的内部空间。在这两种情况下，由于气流下降，在接近窗口处出现了一个较低的温度。案件3，室内的平均温度为29.5。由于房间出现了垂直方向的温度梯度，由于进入的室外空气使房间的上部出现了较高的温度区域。在例4中，温度分布与第2种情况十分相似，但温度分层比较清晰。与第3种情况结果相比，高温区(超过30)不见了，因为热空气被地板空调系统所冷却。4.3 . 相对湿度分布例3的相对湿度分布情况见图9。在案例1，由于辐射板表面温度(19.7)高于露点温度，无结露现象出现。在整个房间中 相对湿度约在45%以上,也表现了相对均匀分布。相比之下，案例2的平均相对湿度为50%左右。因为随着温度的分布，形成了明显的湿度变化。在例3情况中，表面温度的辐射冷却面板(18.3)低于露点温度，而发生凝结的表面辐射小组。即使在送入室外高湿度的空气的情况下，由于辐射冷却系统除去了室外空气的湿度，房间的平均相对湿度可达约61%。相比第3种情况下的结果，例4的平均相对湿度(55%)较低，因为它是由地板空调系统来控制的。4.4 . 空气龄(如图10 )室外空气龄是在流场的基础上计算得到的。通过名义时间常数计算的结果是无量纲常数。在案例1和2中，空气龄为360秒，而在第3和第4中为1200秒。例1由于室外的新鲜空气进入房间的底部，因此在房间的较低部可以观察到新鲜的空气中。例2 与案例1同样可以在附近周边区观察到相同的趋势. 然而，由于地板下的空气流动导致了室内外空气得以充分的混合，因此部分新鲜空气是遍布整个空间的。在这两种情况下,由于新鲜空气与室内空气相混合导致了空气中的一部分变得不新鲜。在3种情况中，室外空气由上部进入房间，相对新鲜的空气分布在房间的上部。在例4中，新鲜空气下沉到房间底部，同案例2 的结果一样新鲜空气是遍布整个房间的。4.5 . 墙体表面温度和人体模型的有效温度和平均辐射温度例1中人体模型的有效温度是28.4，略高于第二种情况(27.7)，拥有相同的PMV值为-0.5。例1中较高的温度导致了较低的相对湿度。由于辐射板表面(19.7)热交换，例1的人体模型的平均辐射温度比例2情况低。即使例3的室内平均温度比例4高，但由于表面温度低，但导致了相同的PMV值。4.6 . 冷负荷的特性自然通风及冷却系统移除的冷负荷祥见图12。例1中，自然通风移除所有的潜热和63%的显热，是案例2的1.3倍。例2的自然通风系统仅能消除部分潜热负荷,而其余的由地板置换通风空调承担，所以该例中地板处置换通风承担的冷负荷是案例1辐射板承担的冷负荷的1.5倍。在夏季条件下(例3和4)，随着冷负荷增加，潜热负荷有个明显的增长，例3中自然通风仅除去少量的显热。但在案例4中，由于室内外空气的混合，大大增加了显热和潜热负荷。地板空调系统移除的冷负荷增长到辐射供冷系统的2.5倍。这样限制室外气流在夏季冷负荷中变得非常重要，夏季换气率理应为最小换气率的3倍。在实际的建筑中,室外气流可以通过空气阻尼器超静态压力状态下控制。综合所有的季节运行情况，混合供冷系统加上辐射供冷的能源比高于地板空调系统。5 . 结论本文描述一种采用辐射供冷与置换通风相结合的新的混合冷却系统，并与使用地板空气供冷相比挖掘它的潜力。当辐射顶板冷却系统采用人工冷却系统时，对于普通季节超过一半的热负荷由自然通风带走。即使在夏天，炎热和潮湿的空气引入室内，穿过上部的空间，由于室内空气的密度差，不与室内下部的冷空气混合。这样，才能实现高效局部的冷却任务。结果表明,在所有的季节，在引入置换通风的前提下，该辐射冷却系统能源效率高于地板空调系统。参考文献1国际能源机构35号,新建或改建办公和教育建筑中的混合通风，国际能源机构预测, 1998 . 2 S. Kato, et al.基于自然和机械通风办公楼的混合空调系统,室内空气99 ( 1999 ) 404 - 409 . 3 E.F赫尔穆特.卡诺纳.斯泰丘,空调供冷初步评估,能源及建筑物22 ( 1995 ) 193-205 . 4 R.J. de Dear, G.S. Brager, 理解以热舒适性方式的报告,美国ASHRAE RP-884,悉尼, MPRL,1998 . 5 S. Murakami, S. Kato, T. Kim,基于辐射和空调控制耦合模拟室内冷/热负荷分析对流,建筑与环境, 36 ( 2001 ) 901-908 . 6 S. Murakami, S. Kato, J. Zeng, 辐射和水分结合从人体散热模拟气流,建筑与环境, 35 ( 2000 ) 489-500 . 7 P.O. Fanger,热舒适,丹麦技术出版社, 1970 . 8 S. Kato, S. Murakami, 基于特殊分配污染物新的通风效率数值模拟, 美国ASHRAE交流, 94 ( 2 ) ( 1988 ) 309-330 .Energy and Buildings 36 (2004) 12731280Radiational panel cooling system with continuous natural crossventilation for hot and humid regionsDoosam Song a , Shinsuke Kato b,a Department of Architectural Engineering , Sungkyunkwan University, 300 Chun chun-dong, Suwon 440-746, Koreab Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, JapanReceived 8 April 2003; accepted 18 July 2003AbstractThis paper investigates a hybrid cooling system, utilizing wind-driven cross ventilation and radiation panel cooling in an office setting .The characteristics of the indoor environment are examined using computational fluid dynamics (CFD) simulation, which is coupled with a radiation heat transfer simulation, and HVAC control in which the PMV value for a human model in the center of the room is controlled to attain the target value.The system is devised with an energy-saving strategy, which utilizes stratified room air with a vertical temperature gradient. The cooled air settles down within the lower part of the room, while the hot and humid air passes through the upper region of the room, sweeping out the heat and contaminants generated indoors. This strategy is found to be quite energy-efficient in the intermediate seasons of spring and autumn in Japan. Even under hot and humid outdoor conditions, the hybrid system coupled with radiation cooling would bring significant energy savings are possible compared with a hybrid system coupled with under floor air-conditioning.1. IntroductionWind-driven cross ventilation is considered to be a promising energy-effective strategy, since it utilizes natures power. Adjusting the indoor environment by natural cross ventilation was the traditional method in hot and humid regions of Asia including Japan. However, in modern buildings, where certainty, reliability, and efficiency are preferred, the use of wind-driven cross ventilation alone is inadequate.A hybrid air conditioning system with controlled natural ventilation, or a combination of natural ventilation with mechanical air conditioning is considered to be able to overcome the deficiency of wind-driven cross ventilation ,and has significant energy-reducing effects .Many studies have been conducted on natural ventilation systems and hybrid air-conditioning systems in Europe and Japan。In Japan in particular, a hybrid cooling system ,using under floor air conditioning incorporating natural ventilation is primarily used。But many studies have discovered that radiation cooling is more effective than conventional air-cooling systems in many areas。In this study, we advocate a hybrid cooling system using natural ventilation and radiation panel cooling. It is based on the concept of utilizing both natural ventilation and radiation panel cooling, aiming to introduce outdoor air into the indoor spaces by cross ventilation and to achieve comfortable indoor thermal conditions by the power of nature as far as possible.Even though it is impossible for a higher outdoor temperature to cool a room by cross ventilation, outdoor air can still be introduced and pass through the upper part of the room, expelling out the heat and contaminants generated indoors. In the meantime, with the aid of a vertical thermal gradient, the lower part of the room can be further cooled by radiation cooling panels installed in the lower part of the room. This strategy is expected to be energy-efficient and to provide adequate thermal comfort in the room. In this paper, the concept of a hybrid cooling system is described and the measured results for the cases where outdoor air temperature and relative humidity are 21 at 60% and 30 at 70% are shown.2. Concept of radiational cooling system with continuous natural cross ventilationFig. 1is a conceptual diagram of the system suggested in this study. This cooling system has a ventilation opening in the upper part of the room to provide ventilation to the indoors by cross ventilation and to discharge internal heat generated in the room. Dehumidifying radiation panelsare installed in the lower part of the room to regulate indoor humidity and to provide cooling. Even when outdoor temperatures become too high to cool the indoors, heat and contaminants generated within the room maybe discharged by cross ventilation from the upper part of the room without significantly disturbing the occupied zone (or task zone) ,and radiation cooling panels installed in the lower part of the room would locally cool the occupied zone only.Thus the proposed system does not ignore the possibility of adjusting the indoor environment using natural power, but maximizes its use to maintain the indoor environment at a comfortable level and to save energy. 3. Outline of CFD analysisAnalysis of room modelThe hybrid cooling system may be used in both residential and office buildings. Here, the case of an office building is examined. The office setting is shown in Fig. 3. The depth of the room is 10.8 m. The width of the analyzed area is set at half of the 3.6 m office module (1.8 m), to make a symmetrical configuration. Hybrid cooling is modeled as the outdoor air flows into the room from the upper opening of the window (0.5m 1.8m; Fig. 3, left), and is expelled through the opening on the other side (0.5m 1.8m; Fig. 3, right), while the radiation panel cooling is still operating. The radiation panels set in front of the desks in the room serve as partitioning panels, and can be operated below the dew point temperature. Whereas in the case of a hybrid cooling system coupled with under floor air conditioning, the cooled air is supplied by diffusers from the floor and returns through out- let air grills in the ceiling. People, lighting, personal computers, solar heat gains, etc to generate a cooling load, which is removed by natural cross ventilation, and radiation cooling or under floor air conditioning. A human model is placed in the center of the room as the thermal comfort sensor. 4. Results4.1. Flow eldsThe flow fields for the different cases are shown in Fig. 7. In Case 1 (natural ventilation-radiation panel cooling), owing to the considerable temperature differences between the indoor air (26.6C) and outdoor air (21C), the negative buoyancy effect on the inflowing air is apparent. The inflowing air flows downwards to the window side, and mixes with the indoor air in the lower part of the room. Though not shown here, the air cooled by the radiation panels flows down to the floor.In Case 2 (natural ventilation-underflow AC), the inflowing air shows the same tendency as in Case 1. However, this air mixes with the under floor AC and ascends toward the upper part of the room. Owing to the vertical temperature difference in the room, a clockwise circulating current is generated on the inner side of the room. In Case 3, since the temperature difference between the indoor and outdoor air (30C), is small, the negative buoyancy effect of the inflowing air is not apparent. With the taller cooling panel, thermal plumes rising from the personal computers can clearly be seen (Fig. 7(c). This is because the average temperature in the task zone drops. But in Case 4, owing to the vertical temperature difference, the outdoor air descends to the floor.4.2. Temperature distributionsThe temperature distributions for the four cases are shown in Fig. 8. In Case 1, the average indoor temperature is 26.6C, somewhat higher than for Case 2 of 24.4C. However, the vertical temperature difference is slight at about 2C. In Case 2, due to the somewhat low velocity (0.8 m/s)of the under floor AC, the temperature near the floor drops to almost 20C. As a result, the vertical temperature difference in the room is steep at about 6C, especially in the inner zone of the room. In both cases, due to the descending currents of incoming air, a rather low-temperature region appears near the window. In Cases 3, the room average temperature is 29.5C. There are vertical temperature gradients in the room, and a high-temperature region is seen in the upper zone of the room because the incoming outdoor air stays there. In Case 4, the temperature distribution is similar to that for Case 2, but the temperature stratification becomes comparatively clear. Compared with the results for Case 3, the high-temperature zone (over 30C) disappears because the hot air is cooled by the under floor air conditioning.4.3. Relative humidity distributionOnly the relative humidity distribution for Case 3 is shown in Fig. 9. In Case 1, since the radiation panel surface temperature (19.7C) is higher than the dew point temperature, no condensation occurs. The relative humidity in the room air is about 45% over the whole space and indicates a relatively uniform distribution compared to Case 2. In Case 2, the average relative humidity is about 50%.As with the temperature distribution, a sharp humidity stratification is formed. In Case 3, the surface temperature of the radiation cooling panel (18.3C) is lower than the dew point temperature, and condensation occurs on the surface of the radiation panel. Even after introducing high-humidity outdoor air, the average relative humidity in the room reaches about 61% because the radiation cooling panel dehumidifies the humid outdoor air. Compared with the results for Case 3, the average relative humidity in Case 4 (55%) drops because it is controlled by the under floor air conditioning.4.4. Age of air (Fig. 10)The age of the fresh outdoor air is calculated based on the resulting flow fields. The calculation results are non-dimensionalized by the nominal time constant. In Cases 1 and 2,tnis 360 s, and in Cases 3 and 4 it is 1200 s. In Case 1, young air is observed in the lower part of the room because the fresh outdoor air moves into the bottom of the room. In Case 2, the same tendency is observed near the perimeter zone with Case 1. However, somewhat younger air is distributed over the whole space, because the outdoor air mixes well with the indoor air due to the air current from the under floor AC. In both cases, the air in the inner part of the room becomes old, owing to the fresh outdoor air mixing with the indoor air.In Case 3, due to the outdoor air flow in the upper part of the room, relatively young air is distributed in the upper part of the room. In Case 4, young air descends toward the bottom of the room, and relatively young air is distributed over the whole area as for the results of Case 2.4.5. Wall surface temperature and OT&MRT of human model (Fig. 11) The OT (operative temperature) for the hum