Investigation of Thermal Effects of CO 2 on Earth-Atmosphere System

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1 Investigation of Thermal Effects of CO 2 on Earth-Atmosphere System Design Team Casey Bennett, Mark Corriere Jonathan Hammel, Nicholas Hodson Andranik Valedi Design Advisor Prof. Yiannis Levendis Y.levendis@neu.edu Abstract Increased levels of carbon dioxide, methane and particulate matter in the atmosphere, resulting mainly from combustion of hydrocarbons, are suspected to adversely affect the Earth s atmosphere. An experiment was proposed to illustrate the effects of carbon dioxide on global warming. The design includes a cylindrical vessel (simulating the Earth s atmosphere) for containment and control of the relative concentrations of CO 2, a near-infrared emitter (simulating the sun), a specimen (simulating the Earth), and a robust data acquisition system for recoding variables of interest. According to theory, by increasing CO 2 concentrations, more energy is trapped by the CO 2 and hence the temperature of the atmosphere and Earth will increase. The experimental apparatus has been designed to facilitate the investigation of the effects described above. The temperature and CO 2 concentration will be recorded in order to determine if there are correlations between them. Some design aspects of particular importance are those related to the heat loss out of the system and geometric considerations.

2 The Need for Project The work entailed here will serve as a cornerstone of further research into the thermal properties of carbon dioxide, and ultimately their role in the behavior of Earth s atmosphere. The experiment will address the lack of demonstration units to aid the study of climate change. Experimental data is a critical component of any physical study, and currently there is a lack of experimental setups designed to investigate the basic phenomena involved in climate change. The data collected and correlations observed are intended to shed light on the phenomenon of global warming. The Design Project Objectives and Requirements The ultimate objective of this Design Objectives project is to draw experimentally In order to understand the relationship between CO2 concentrations based conclusions in regard to the and temperature changes at the surface of the Earth the fundamental significance of CO 2 relationship between CO2 concentrations, absorption of radiation and concentrations on changes in an temperature must be explored. The focus of this project is to atmosphere s temperature. experimentally measure, record and analyze relations between CO2 concentrations in an atmosphere and temperature changes of a surface exposed to that atmosphere and of the atmosphere itself. Design Requirements The experiment intends to explore the correlation between CO 2 concentrations within the atmosphere to temperature rise in the region of the surface of Earth. As a requirement, this project delivers a set of empirical data and a physical experiment that can be easily expanded and modified. The deliverable of the project encompasses a physical experiment/portable-scale demonstration.

3 Design Concepts considered Three major candidate design Three design candidates for the experiment were considered: concepts were considered; only small-scale spherical, control volume with differential analysis, and one met the full range of design columnar control volume. criteria. Small-scale Spherical An initial prototype allowed for a preliminary investigation of the needs of the future design. Gas is introduced and contained in a spherical glass flask (of 6 inch diameter); a black sphere centered in the flask acts as an absorptive and emissive surface. A thermocouple monitors surface temperature. The model served as a first iteration and helped to identify problems with the design. The most noticeable issue Figure 2: Small-scale Spherical was the short optical depth associated with the flask; this allowed inadequate radiation to be absorbed and hence required temperature sensors with impractical levels of accuracy to measure such small temperatures changes. Control Volume with Differential Analysis The design was comprised of two equal control volumes (CV) of gas situated symmetrically about conductive plate. A temperature difference would be induced between the two CV of gas by varying the concentration of CO 2 in one of the CV and hence triggering an energy flux across the plate. This concept was later abandoned because of its impractical size and number of components. Single Columnar Control Volume The design utilizes its entire length in absorbing radiation from a source. A sample specimen (representing Earth) and radiative source (representing the sun) are mounted at opposing ends of the CV; thermocouples are mounted along the length and at the specimen to measure thermal effects on the gas and surface. A data acquisition system is used to monitor the temperature changes as CO 2 concentrations are varied. Figure 3: Single Columnar Control Volume

4 Recommended Design Concept The design was created from A single design was created from the extensive mathematical mathematical considerations and analysis and intermediate prototyping. The design meets the intermediate prototyping. The requirements of a modular, easy to use experiment with a sufficient design meets the requirements of optical depth to ensure that varying CO 2 concentrations will induce a a modular, easy to use experiment measurable temperature change. with optical depth sufficient to Design Description induce measurable temperature The design s main component is a 3-foot polycarbonate tube changes upon varying CO 2 surrounded in 1 in. thick polyurethane foam insulation to minimize concentrations. the heat loss to the environment. A specimen to be irradiated is attached by means of a flange and mounting collar on one end, while on the other end an acrylic window is affixed in the same manner. Both the acrylic window and the specimen are sealed to the tube via a neoprene gasket. Clamping pressure for the seal is accomplished through a bolted connection between the flange and collar. A pair of v-blocks are attached to the base of the experiment, providing both a means of fastening and centering the tube. Radiation is provided to the specimen by means of a 175 W nearinfrared heat lamp attached 6 inches from the acrylic window. An aluminum shroud encompasses the heat lamp and acts as protection from contact burns and potential eye damage. The tube is wrapped with a reflective aluminum tape to direct the maximum amount of radiation to the specimen. The controls for running the experiment and gathering data are all housed in a central location behind the radiation source. Housed within the control box are the knobs for filling and purging the tube, regulating pressure and flow of the CO 2, and reading the 4 thermocouples distributed along the length of the tube. The flange and collar assembly allows for quick and easy changes of specimen material with only the use of simple tools. Analytical Investigations The major requirement for this experiment to be viable is the length of the tube. The length of the tube is the path length that the radiation emitted by the specimen will travel through and is directly related to the amount of temperature change that will be induced by varying CO 2. A well-established radiative heat transfer correlation

5 Financial Issues The final experimental design cost under $600 to build. Recommended Improvements was implemented to predict this length (Hottel, 1967). However, in the event that the length is insufficient to induce a temperature change, the modularity of the experiment will allow for adjustment of this key parameter. Key Advantages of Recommended Concept The major advantage of the design is the modularity of the key components and parameters. First, the flange and collar assembly allows for quick and easy changes of specimen material with only the use of simple tools. Second, the adjustable v-blocks provide for accommodating varying tube lengths in the event that the optical depth of the experiment needs to be quickly changed. Also, the heat lamp utilizes a standard light bulb socket, allowing for the variation of both the power of the source and the wavelength. Perhaps most importantly, the experiment allows for introducing multiple types of gases, as well as water vapor and aerosols simply by adding additional inlets to the tube walls. This adjustability provides for an exceptionally adjustable device for a multitude of climate change investigations. This experimental apparatus is a single device and will not be reproduced. The modularity of the design allows for the reuse of many of the components purchased. Some components of the design were procured for free from resources within the University. Any costs associated with this design are one time and the total cost of the experiment is under $600. By making the recommended improvements presented to the This experimental apparatus could be improved through the addition of a data acquisition board with more channels for right the experimental would be simultaneous measurements of temperature from multiple better suited to make definitive thermocouples. Another area for improvement would require the conclusions in the current investigation and to be adapted for further research. inclusion of a high-resolution device for the measure of CO 2 concentrations from 0 to 100%. The cost of such components was preventative within the current design.