"Wisdom begins in wonder" – Socrates
Tag: Thermodynamics
Quasistatic Processes
07/14/18
“Can a thermodynamic process be so slow that it’s almost static?”
Thermodynamic processes can happen over any period of time. Sometimes they happen so slowly that they almost seem to be static. These Quasistatic Processes are often used in analysis of Iso-Processes due to their stable nature.
Isovolumetric Processes
06/30/18
“What happens when a thermodynamic system does not change its shape?”
When a thermodynamic process does not change the system’s volume, it is known as an Isovolumetric Process. Since the volume is held constant, the total work done ( W = PdV) by the system will be equal to zero.
Isenthalpic Processes
06/28/18
“Are there thermodynamic processes that take place without any change in enthalpy?”
Isothermal, isobaric, and isovolumetric (constant volume) thermodynamic processes are very well known. But there are also Isenthalpic Processes which occur when there is no change in Enthalpy for the system. The throttling process is a common example of an Isenthalpic Process.
Transmissivity
05/04/18
“How can radiation pass through a material?”
When radiation strikes an object, much of is reflected off or absorbed by the material. However, sometimes part of it is able to go through everything unimpeded! This value is known as the transmissivity of an object and is an inherent property of a material.
Heat Flux
04/21/18
“How can we classify heat flow without knowing the area?”
Heat flow is usually thought to be how fast heat can be transferred through a given volume. However, sometimes we may not know about the surface area of our system. So how can we use our scientific mindset to find out? Well, what if we were to simply make a new property, which only classified heat flow for a given length? This is known as a Heat Flux and is applied in engineering systems all over the world.
Prandtl Number
04/12/18
“How can we quantify the ratio between momentum and thermal diffusivity?”
For fluids flowing over an object’s surface, momentum and heat will be transferred, oftentimes at different rates. How quickly one changes with respect to the other will completely affect its properties. As a result, engineers have devised something known as the Prandtl Number, which compares the diffusivity of momentum and heat as a ratio, symbolized as pr = c_p*Mu/k with C_p being the specific heat capacity of a gas at constant pressure, Mu being the dynamic viscosity and k the thermal conductivity.
Thermocouple Reference Junctions
03/19/18
“How can we properly calibrate thermocouples?”
Thermocouples are very useful for measuring temperature differences due to their quick response times and low costs. However, in order to operate accurately, they must be connected to a zero degree reference point. So how can we use our engineering knowledge to solve this? Well, what if we were to simply connect the thermocouple leads to copper wires in ice water. These would create reference junctions in which the thermocouple leads would be compared against values at 0 degrees Celsius. This system calibrates the thermocouples to much greater accuracy, but extra care must be taken.
The Critical Radius
02/18/2018
“What is the most optimal radius for insulation?”
It is usually thought that if one wants to provide more insulation to an object, then all they have to do is add more layers. However, if this also increases the surface area of an object, which can cause the heat loss by convection to increase as well. If the insulation becomes too large, then the convection effect actually takes over! So how can we find the most optimal radius for convection? Well, if we use our knowledge of heat transfer and calculus, then we can find out that the critical radius r for a cylinder is equal to k/h and 2k/h for a sphere, where k is the conductive heat transfer coefficient and h is the convective heat transfer coefficient.
R-Values (Construction)
01/21/18
“How can we measure a building material’s resistance to heat flow?”
One of a building’s primary functions is to insulate people from the outside world. And just as different materials are made of different atoms, different building materials are more efficient at producing insulation. So how can we quantify this? Well, let’s start by testing each material and assigning it a particular value. Engineers have done this and came up with the concept of the R-value. If you take a material of R-value x and one of R-value y and place one in front of the other then you will obtain a material with an R-value x + y. R-values are one of the fundamental components of modern-day construction
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