Akio Ishii

Full-scale measurements and wind tunnel tests on cross-ventilation

Abstract This paper describes the full-scale measurements and the wind tunnel model tests on cross-ventilation induced by the natural wind and the similarity between them. The full-scale measurements were conducted in a group of apartment houses under the condition that the direction of the approaching wind to the objective site was almost constant. The air flow speed around the objective buildings and the indoor air flow speed caused by the cross-ventilation are measured in the full-scale measurements. The wind tunnel tests consist of two kinds of experiments. One is the experiments on the air flow around buildings and the wind pressure on building surfaces as the source power of the cross-ventilation. The other is the experiments on the distribution of indoor air flow. Each of these experiments needs each experiment model. Their results are compared with the full-scale measurements.

Field surveys on cooling effects of vegetation in an urban area

Abstract 1. 1. Three kinds of field survey on different scales were carried out in Fukuoka City in summer to examine the relationship between the quantity of vegetation and air temperature. 2. 2. The field of the largerst scale measurement is across the city. 3. 3. Several parks and shrines of various sizes in the city were selected as other measurement areas. 4. 4. The most detailed measurements are carried out in a park with an area of 1.25 ha located in a down town area of the city. 5. 5. Though the amount of vegetation is expressed in a unique way in each survey, it is clearly found that the greener it is, the lower is the air temperature.

Investigation and numerical simulation of the wind effects on thermal comfort in a house

Abstract Full-scale measurement of indoor thermal factors and numerical simulation of indoor air flow are presented in this paper. The measurement was carried out in summer in two dwelling units of an apartment building; one was ventilated naturally through opening windows and the other was unventilated. Indoor thermal conditions of these two houses were estimated by the predicted mean vote and compared to find that the thermal conditions in the ventilated house ranged in the comfort zone while it was in the hot zone in the unventilated house, which depended upon the indoor air flow speed. Numerical simulation of indoor and outdoor air flow of a single unit house was carried out to predict the air flow speed by natural ventilation through opening windows. Multi-mesh system and k-a 2-equation model were applied for the indoor and the outdoor turbulent air flow for which the scales were greatly different.

Cooling effects of a river and sea breeze on the thermal environment in a built-up area

Abstract Two kinds of field observation are carried out to examine the cooling effects of a river and a sea breeze on the thermal environment in a built-up area in summer. One is the measurements along a river and an avenue which go in the direction of the sea-land breeze. The other is the measurements along a street nearly perpendicular to the river. The wind speed above the river is larger than that above the street when the sea breeze blows, while the air temperature above the river is clearly lower than that above the avenue. The air temperature difference between them falls less downstream of the sea breeze. The air temperature in the space between buildings is the highest in the street and that at the cross point is the next; the wind direction is close to that of the sea breeze. Even if the paths are rather narrow, the ventilation effect by the sea breeze is clearly recognized.

A comparison of field surveys on the thermal environment in urban areas surroundings a large pond: when filled and when drained

Abstract This paper describes the thermal effect of a pond with an area of 127 000 m2 on the surrounding built-up area. Two surveys were conducted and compared, when water filled the pond and after the pond was drained. Moreover, two similar surveys were carried out in the extended area. In the water-filled case, the air temperature distribution demonstrated that a clear cool island was caused by the pond. In the afternoon, it was most prominent with a temperature differential of about three degrees between the center of the pond and the far outside streets, and it extended about a few hundred meters leewards. In the water-drained case, a cool island, caused by the wet bed including water pools left in the leeward half of the pond due to incomplete drainage, diminished with half the differential.

Observations of heat flux in an urban area with a large pond by kytoons

Abstract There are few studies on the thermal environment in urban areas, considering the convective heat flux by natural wind and covering materials on the ground surface. In this paper, the heat flux is calculated from the profiles of the wind speed and the air temperature, which are simultaneously observed by kytoons at three points in an urban area with a large pond, to examine the difference between the built-up area and the water surface, and to make clear the relation between the convective heat transfer and the wind speed.

An experimental study on the effect of humidity on thermal sensations of people in summer

Abstract 1. 1. The authors propose humidity reduction instead of lowering room temperature in order to reduce cooling syndrome. 2. 2. They conducted experiments with subjects in the rooms, one with controlling humidity to about 40% r.h. and another without humidity control. Air-conditioning system with humidity control has a greater promise in making a comfortable environment, even at the temperature as high as 30°C, in comparison with conventional means using temperature control alone. 3. 3. Relationship of actual mean votes on temperature sensation and comfort sensation with PMV and SET, respectively, suggests that Japanese people might be more sensitive to humidity than Westerners and so different methods from those used in the western countries should be required for human thermal environmental studies with respect to the hot humid summer in Japan.

Statistical analysis of the sea-land breeze and its effect on the air temperature in summer

Abstract The sea-land breeze is a characteristic phenomenon of seaboard areas. Because the air temperature of the sea breeze is lower than that of the land breeze, the sea breeze can have a useful cooling effect during hot summers on the seaboard area. Statistics of wind and air temperatures in and around a seaboard city, Fukuoka, Japan, in summer are presented to describe the effects of the sea-land breeze on urban thermal environments. Statistical data for wind direction, wind speed and air temperature taken every 10 min on sea-land breeze days, i.e. days when both sea and land breezes appear, indicate that the sea breeze mitigates the rise in air temperature during the daytime. The time shift between land breeze and sea breeze is a dominant factor on fluctuations in air temperature of the area, and it depends on the distance from the coastline.

Statistical analysis for the characteristics of sea-land breeze and its effect on urban thermal environment

Abstract This study has two aspects to clarify the effect of the sea-land breeze on urban thermal environment. One is the statistical analyses of meteorological data in Japan to indicate the general characteristics of sea-land breeze in summer. The other is the field observation to show the relation between air temperature and the sea-land breeze. The summer term is decided from the 7-day moving average of diurnal mean air temperature. The characteristics of the sea-land breeze are expressed by the sea-land breeze component which is the vector component of a wind vector in the main direction of the sea breeze. The average sea and land breeze vectors obtained from all the analyzed data are compared with those calculated from the data selected as the sea-land breeze days. The time lag of the wind shift by the distance from the coastline clearly appears in the observed data. It is also found in the observed data that the increase of the air temperature falls when the wind shifts from the land breeze to the sea breeze.