Temperature Profiles of Sunlight-Exposed Surfaces in a Desert Climate: Determining the Risk for Pavement Burns

Abstract

Plentiful sunlight and high temperatures in desert climates cause burn injuries from contact with sun-exposed surfaces. The peak temperature, times, and surfaces of greatest risk are not well described. This work recorded temperature measurements of six materials in a desert climate. Surface temperatures of asphalt, brick, concrete, sand, porous rock, and galvanized metal were measured throughout the summer, along with ambient temperature, and sunlight intensity. Samples were placed in both shade and direct sunlight for evaluation of sunlight effect. Seventy-five thousand individual measurements were obtained from March to August 2020. Maximum recorded temperatures for sunlight-exposed porous rock were 170°F, asphalt 166°F, brick 152°F, concrete 144°F, metal 144°F, and sand 143°F, measured on August 6, 2020 at 2:10 pm, when ambient temperature was 120°F and solar irradiation 940 W/m2. Sunlight-exposed materials ranged 36 to 56°F higher than shaded materials measured at the same time. The highest daily temperatures were achieved between 2:00 and 4:00 pm due to maximum solar irradiance. Contour plots of surface temperature as a function of both solar irradiation and time of day were created for all materials tested. A computational fluid dynamics model was created to validate the data and serve as a predictive model based upon temperature and sunlight inputs. This information is useful to inform the public of the risks of contact burn due to sunlight-exposed surfaces in a desert climate.

Figure 1.

Photographs of experimental data collection set up in direct sunlight (top) and in shade (bottom). This arrangement was placed on the roof of the Thomas T. Beam Engineering Complex on the campus of University of Nevada Las Vegas. Six different material samples were arranged including porous rock (top left), asphalt (top middle), sand (top right), galvanized metal (bottom left), concrete (bottom middle), and brick (bottom right). All but the galvanized metal were placed in a wooden form measuring 2′ × 2′ and 3.5 inches high. Thermocouples were placed on the surface of each material and held in place with adhesive. Sunlight intensity was measured using a pyranometer which is seen in the lower left corner to the left of the galvanized metal.

Figure 2.

Twenty-four hours Average surface temperatures of each surface recorded throughout the study period in shade and direct sunlight.

Figure 3.

Daily measurement of asphalt surface temperature (F) and hour of each day for a 1-week period from August 14 to August 20, 2020.

Figure 4.

Risk contour plots showing surface temperature (F) of each material measured based upon solar irradiance (W/m²) and ambient temperature (F).

Figure 5.

Risk contour plots showing surface temperature (F) of each material measured compared with solar irradiance (W/m²) and hour of the day.

Figure 6.

Computational fluid dynamics model equations for all six surfaces and temperature prediction equations based upon ambient Temperature (T_A) and Irradiance (I). Representative comparison plot of Asphalt data compared with CFD model predicted data.