Hisaya Nagai

A ventilated courtyard as a passive cooling strategy in the warm humid tropics

The paper investigates the potential of a courtyard for passive cooling in a single storey high mass building in a warm humid climate. The inclusion of an internal courtyard in building design is attributed to the optimization of natural ventilation in order to minimize indoor overheating conditions. However, the efficiency of this strategy greatly depends on the design details of the building composition in providing appropriate airflow pattern to the courtyard. From the results of thermal measurements, a significant correlation between wall surface temperatures and indoor air temperatures is evident. A reduction of indoor air temperature below the levels of ambient is seen as a function of heat exchange between the indoor air and high thermal mass of the building fabric. However, this behavior is affected by indoor airflow patterns, which are controlled through the composition between envelope openings and the courtyard of the building.

Indoor Thermal Modification of a Ventilated Courtyard House in the Tropics

Abstract This paper investigates the effects of airflow patterns and airflow rates on thermal behavior of a ventilated courtyard building in a warm humid climate. With some airflow patterns indoor air temperature can be brought to a level below the ambient, while with others the indoor air temperature may be higher than the ambient. The integration of a courtyard in the building design can optimize indoor airflow and is of significant importance with regard to the indoor thermal environment provided the courtyard maintains correct contacts with the outdoor environment. The current paper explores airflow patterns and airflow rates in a modern tropical courtyard house in respect to corresponding indoor thermal modifications. A thermal investigation was carried out on the site by manually changing the composition of airflow inlets (openings) found in the building envelope. From the results it is observed that the different airflow patterns affected different thermal environments and sometimes a cool condition within the courtyard and in the surrounding indoor spaces. Relatively low indoor air temperature was observed with a particular air movement pattern created through the openings found on a longitudinal horizontal axis through the courtyard. The temperature was below the ambient by 1.3 degree C with an airflow range of 1.5 to 2.0 air changes h-1.

Study on the Heat Load Characteristics of Underground Structures

Abstract This study is being conducted to clarify the heat load characteristics of underground structures. The authors have sought to achieve this by clarifying the heat and moisture behavior of an underground basement and surrounding ground, and acquiring basic data for computational analysis. This paper presents measurement results acquired over approximately one year of field experiments on an underground experimental basement under internal heat generation conditions, commenced in October 2004. The authors also present the results of analyses on the heat and moisture behavior of the experimental basement and ground, the influence of internal heat generation on the surrounding ground, the condensation behavior, the interrelationship between precipitation and the fluctuation of moisture content in the ground, the annual mean heating load per unit area, and other factors.

Study on the Heat Load Characteristics of Underground Structures Part 2. Computational Analysis of the Heat/Moisture Behavior and Heat Load of Underground Structures

Abstract This study was conducted to clarify the heat load characteristics and heat and moisture behavior of underground structures. The authors achieved this by carrying out a numerical analysis using simple heat diffusion and simultaneous heat and moisture transfer equations based on measurement data reported in a previous paper (Park et al., 2006). This paper presents the results of a numerical analysis on the heat load characteristics and heat and moisture behavior of an underground basement and its surrounding ground under a condition of internal heat generation. The authors found it difficult to predict the heat behavior and heat load of the underground basement by simple heat diffusion alone. Accurate prediction of the thermal environment and heat load requires careful consideration of the influences of moisture and precipitation.

Reducing Effect of Latent Heat Load by Fresh Air Heat Load Reduction System Using Underground Double Floor Space

Abstract This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space. The fresh air is introduced into the double slab space and passes through the opening bored into the footing beam. The air is cooled by the heat exchange with the inside surface of the double slab space in summer, and heated in winter. Then the heat is transferred to the adjacent soil through foundation slab, wall and to the room just above the mat through floor slab. This system not only reduces sensible heat load of the fresh air by heat exchange with earth but also reduces latent heat load of the fresh air by ad/de-sorption of underground double slab concrete. In this paper, we used a model for evaluation of fresh air latent heat load reduction by hygroscopic of air to earth exchange system taking into account coupled heat and moisture transfer of underground double floor space. In conclusion it shows the validity of the proposed method for a design tool and the quantitative effect of the system.