The Impact of Shelter Related Factors on the Natural Ventilation, and thus the Indoor Thermal Comfort in Refugee Camps - A Case Study of Kutupalong Refugee Camp in Bangladesh
The purpose of this study was to evaluate the ability of the three different shelter conditions in achieving natural ventilation to improve the indoor thermal comfort level in Kutupalong (KTP) Refugee Camp in Bangladesh. The three shelter conditions were 1) shelter spacing; 2) shelter orientation; and 3) ground sloping conditions. Also, in the absence of favourable conditions, a feasibility study using a wind catcher to improve the wind at occupant level was provided.
The thermal comfort level defined by the achieved discomfort hours was derived from the adaptive thermal comfort analysis, which included the analysis of adaptive thermal comfort model and weather (humidity and wind) adjustments equations. The adaptive thermal comfort model and the wind adjustment equation used in this study was developed by Humphreys in 1978 and 1970, both of which studies Nicol examined in 2004. Two humidity adjustment equations: ISO7730 and the MacFarlane study were applied and compared. The most favourable conditions for achieving thermal comfort were identified by comparing the current and predicted thermal comfort levels in different conditions.
The current level of thermal comfort was achieved by obtaining the comfortable temperature from the adaptive thermal comfort model and adjusted with the humidity data in the weather file. The wind factor was not encountered in this stage because of unavailable data. A +/-2.5oC of the comfortable temperature range was applied to achieve an acceptance level of 80% among shelter occupants. The results showed that the level achieved before and after the consideration of humidity effects were from 16% to 22% (ISO7730) and 26% (MacFarlane) respectively, i.e. the current level of thermal comfort. The MacFarlane study was found to be more sensitive to the effect of humidity on comfort levels.
Four cases were derived from different conditions and simulated by CFD analysis with constant wind speed at 6m/s in eight different directions. An OpenFOAM plugin to Grasshopper in Rhino was used as CFD software and was validated with AIJ benchmark test before application. The outcomes of this were compared according to different conditions, and a further CFD analysis was undertaken to achieve the indoor airflow.
After developing the links between the wind speed (i.e. 6m/s) with eight different directions, the different conditions and their respective indoor airflow, these were integrated into the weather data of KTP camp. The results showed that the outcomes achieved with or without integration of weather data were almost the same except for shelter orientation: 3m shelter spacing model and single-sided sloping ground was better to achieve higher inward airflow. No preference orientation was found in the case in which real weather data were not considered. But after weather data integration, all orientations except East were preferred, subject to other conditions. The ground sloping conditions (i.e. single-sided sloping ground) might also have potential priority influence in achieving indoor thermal comfort in the KTP camp.
The study of the wind catcher was in two parts: CFD simulations to identify the better wind at high level (6m height above ground) when there was low wind at occupant level (1m height above ground); and, the site measurement conducted in KTP camp to demonstrate the capability of the wind catcher in divering the high level wind to occupant level. The positive outcomes of both parts of the wind catcher study indicated that the installation of a wind catcher might able to improve the natural ventilation at occupant level.
Throughout the study, the shelter conditions such as shelter spacing, orientation and ground sloping conditions were able to improve natural ventilation to a certain extent and could thus achieve better indoor thermal comfort for occupants in the KTP refugee camp. Without the favour of these conditions, however, installing a wind catcher might able to help in providing the natural ventilation required at occupant level.