The transfer of heat and mass happens all around us every day. Many of the appliances and process that we encounter daily function as a result of heat transfer concepts. Being in this class has taught me how to understand basic concepts of heat and mass transfer as well as how to apply them to biological and environment systems.
For example, many people including myself enjoy having a nice hot cup of coffee or tea in the morning. Somedays I pour the piping hot tea into my tumbler, and throughout my day it stays so hot that I can't even drink it. One would think that by the end of the day my drink would be cooled, but by explaining Thermal Resistance I can explain why that did not happen. One of the first things I was taught were the three modes of heat transfer which are convection, conduction, and radiation. The process of heat escaping my cup would be conduction, which is the transfer of heat from one substance to another. Tumblers have several layers separating the drink from the air, and the thermal resistance of those layers can be described in the following formula:
With this equation each layer of the cup provides resistance, so the total resistance is the sum of each layers resistance. The higher the thermal resistance the lower the rate of heat loss will be, so I want my tumbler to have a high thermal resistance so that little heat is lost from my drink.
Another example of heat and mass transfer application would be a heated aquarium. Seahorses enjoy a temperature around 26 degree celsius, if they are living in an aquarium and outside of their natural habitat that temperature would need to be maintained. If we have the outside temperature, desired temperature, specific heat capacity of water, mass of water and wattage of the heater we can determine the amount of time the heater would need to run to heat the water to the desired temperature.
Lastly I always wondered about how certain animals are able to maintain their body temperature in harsh Arctic climates. As it turns out some animals, like the beluga whale, have thick layers of blubber to help keep them warm. Adipose tissue, the tissue that makes up blubber, has a relatively low thermal conductivity. This means that it does not transfer heat as well as other tissues would.
Because of the high thickness (L) and low thermal Conductivity (k), the beluga whale is highly effective at keeping himself warm. I can take this idea and apply it to designing insulation for a building. If the walls of a building are have low thermal conductivity and are able to maintain heat during colder season, it could save the owners money on heating and air.
Many of the concepts we discussed in Heat and Mass were directly related to topics I covered in thermodynamics. This showed me that the knowledge I gained in each of my courses would continue to build and show up in future classes, even if the subject matter is not as in depth as it was the first time I was introduced to it. for instance, in Thermo I learned how to derive the formula for heat that I used above, but in heat and mass I was able to take that formula and apply it to my problems while already understanding it's significance. By understanding these fundamental concepts in Heat and Mass, I will be able to solve practical problems when I begin to work as an engineer and have the tools to do so.
Intro to Sustainability
The topic of sustainability ties in directly with my goal in Biosystems engineering to build a more sustainable society. In this class we spent time covering food systems and the environments. The thing that stuck with me the most from this lecture was that food issues are multifactorial, meaning you cant change one thing without addressing another. For example, say I wanted to decrease the amount of fast food restaurants and increase the amount of farmers markets with healthy options. I would also have to consider how people in food deserts would get access to the farmers market, how can I make the food affordable, what incentives would have to be in place to make people agree with this idea, among many other things. This teaches me that what may seem like one problem is actually many complex problems that are influenced by a multitude of factors. When it comes to critical thinking and problem solving I have to approach issues from as many different perspectives as I can. This is useful for when I help to do tank design with Engineers without borders. I have to consider the terrain the tank is on, how the materials will get to the destination, and what capacity of water the tank need to accommodate.
Hydraulic Transport
I see Labs as a way of taking concepts and information that seems hypothetical and seeing a practical application of it for better understanding. I completed several labs for my fluid Mechanics class that allowed me to get a better grasp on the complex topics we covered. My favorite lab from this class was one I did on rheology, which has to do with the deformation and flow of matter. I used a Bohlin Rheometer to analyze the fluid properties of Soaps, Starchy water, Mayonnaise, and Oil at various temperatures. I was able to graphically analyze the Shear stress, shear strain, and viscosity if each substance. Ultimately this helped me to understand the behavior of Newtonian, Pseudoplastic, and Dilatant fluids. The reason this lab was most interesting to me was because of the analysis of Starchy water. As a child, most of us have dealt with some sort of "flubber" that seems to ooze yet stiffens when you throw it or hit it. After doing this lab and having an idea of what a pseudoplastic fluid is, I know understand the science behind why the fluid behaves as such.
This lab not only taught me about fluid mechanics concepts, but showed me that I can fact check my work when I know the results. Going into this lab I understood what each fluid should behave like and what that may look like graphically. Seeing results that aligned with my knowledge helped to reinforce my confidence in my education.
Click below to have a look at the report I completed for the lab, there you can see more details about my findings.
The concepts and equations used in fluid mechanics have many practical applications to subjects like medicine, energy, and aerodynamics. The fluid mechanics application that I was most curious about was how you could use these formulas and concepts in the field of medicine. In order to solidify my understanding, I gathered my knowledge to explain how topics covered in this class would apply to an insulin pump. An insulin pump is a medical device that can administer insulin to a diabetic person throughout their day with out the need for multiple needle sticks. These devices are accurate and can provide users with peace of mind about their conditions.
When it comes to designing a fluid system, it is crucial to understand the properties of the fluid that will be moving through the system. Density, the mass per unit volume, is a fluid property that we can use in equations to understand how a certain fluid will flow. For this particular device, the density on insulin can allow us to understand how it will behave when injected into the blood.
ρ=m/V (kg/m3) •ρ= density •m= mass •V= volume
The Flow Rate is how fast or slow a fluid moves and is given in volume per unit time. As for how this applies to insulin injects, a persons basal rate of insulin is the volume of insulin they are supposed to receive over a 24 hour period. This will result in a steady flow rate that can be found using the formula below. Once the desired flow rate of the insulin is known, this value can be used in other equations to solve for more useful values.
Q=V/t •Q= flow rate •V = Volume •t = Time
Poiseuille's Law is a formula that involves a pressure drop of an incompressible fluid in laminar flow through a cylinder of constant radius. This accurately describes how a fluid like insulin moves from the pump, through the silicon tubing, and into a persons body. If we know the viscosity and flow rate, assume certain values like the length of the tube and the pressure gradient within. Doing so allows us to solve for the radius of the tube, so now a user of this device know exactly the type of tuning they would need to use for the best results.
Reynolds Number is used to determine if a flow is laminar or turbulent. As I mention before the flow in this tube is assumed to be laminar, and it should be to prevent issues during the injection. This formula allows us to verify that the fluid flows inthe nature that it should. By plugging in the determined values and knowing that for a closed cylinder RE<2300 is Laminar, we can be sure that our system will be operating with laminar flow.
Re=ρvl/μ •ρ= density •v= velocity •l= length •μ= dynamic viscosity
Since this is a battery powered mechanical device the formula for Efficiency can be uses to calculate. By knowing the power supplied by a typical battery and the energy used by the pump, we can figure out how efficient the machine is and how long a certain batter would last when powering the device.
η=E /W •η= efficiency •E= mechanical energy •W= electrical energy
Equations from courses beyond hydraulics have enable me to be able design a fluid system. Two equations in particular come from my Thermodynamics class which dealt with the relationships between heat, work, energy, mass, and temperature. The first law of thermo dynamics states that energy cannot be created, destroyed, or altered in any form. From this fact we can derive two crucial equations: Energy Balance
Conservation of Mass
Both of these equations essentially tell us that when something goes into a system something must come out. The thing that exits could be work, energy in various form, and mass. This is the relationship between energy input and energy output, meaning all energies that enters a system must enter all energies that exit. Knowing this enables us to solve for many values involved in a given system,