Volcano Vaporizer used by Medical Marjuana patients eliminates the potential harm associated with the combustion that results from smoking plant matter. Vaporization yields smoke-free vapor and maximizes therapeutic effect and minimizes extraneous impurities.
Glandular trichomes contain most of the cannabinoids and essential oils responsible for therapeutic effect, aroma & flavor.
Vaporizor Study: Journal of Cannabis Therapeutics 4(1), 2004
Dr. Tod Mikuyira (r.i.p.) - References to Vaporization Studies
Behavior of Vapor (Gases)
For complex smoking device design, an important concept to understand is the Ideal Gas Law. The Ideal Gas Law is a simple equation that lets us predict the behavior of liquids and gases.
That is, pressure (P) times volume(V) is directly proportional to temperature (T). You already knew that gases expand when heated, as do most liquids. Here it is in a useful equation.
Let's consider a closed-system example, a CO2 cylinder. The volume of the cylinder does not change, it is constant. With constant volume we get:
That makes sense. If we heat up the cylinder then the gas tries to expand and the pressure goes up. In the equation, if P goes up, T goes up and if T goes up, P goes up. Conversely, if we open up the valve and let all the CO2 out quickly, the temperature (T) drops quickly, along with the pressure (P). Whenever the tanks are filled the gas inside heats up.
PV~T applies to most systems that involve gases and liquids. That includes the atmosphere and oceans. Although these systems are more complicated, notice how a cold front in the weather is often responsible for rain and low pressure. Lower P is lower T.
Good vaporizor designs consider that PV~T and that water and essential oils vaporizing expand to an exponentially larger volume, from liquid to gas. This affects the overall fluid dynamics of the device and can be critical to success when dealing with small volumes or restricted cavities. Allowing a heated vapor cloud to expand is essential to cooling.
But what is the proper dilution rate for maximum absorption? What is the ideal mixture of air and vapor?
The physiology of absorption of cannabinoids in the lungs is also important to vaporizer design. One principle to understand is that the amount of cannabinoids actually absorbed are dependent on several variables. One of those is the concentration of cannabinoids and another factor, proposed here is internal pressure of the lungs.
Generally, the higher the cannabinoid content of a single vapor cloud inhaled, the more cannabinoids will be absorbed. At some point no additional absorbtion will occur with increased concentration and this surplus is wasted upon exhale. Vaporizors can gain big advantages in efficieny by delivering optimized mixtures of air and vapor. You as a cannabis scientist can work on this problem.
Like concentration working as a driving force that aids cannabinoid absorption, it is proposed that the increased internal pressure of the lungs that results from holding one's breath is an additional driving force that helps [THC] absorption. In chemistry, thermodynamics, physiology and cell biology there is a recurring and important theme that heat, pressure and concentration are the driving forces behind systems - think equilibrium & entropy.
Take for example the carbonation of water or cola. The liquid is placed into a tank and sealed. CO2 gas is added until the system is under ~high pressure and the CO2 gas is forced to dissolve into the liquid. If the pressure of gas is increased, the cola will be over-carbonated as the higher pressure results in the liquid taking on even more CO2.
Similarly, the lungs absorb oxygen better at sea level because the pressure of oxygen is more than on a mountain top. The lungs also facilitate absorption of cannabinoid vapor (mixed gases) into the blood. In the case of hardcore mountaineers like Ed Viesters or Steve House, breathing forcefully through pursed lips to create resistance (pressure) helps 'drive' the oxygen absorption of the lungs.
All of this 'driving-force' talk is based on a basic concept called LeChatlier's Principle. In basic terms it says that systems prefer to be at equilibrium, with things steady and balanced. When the equilibrium is disturbed by an external force, the system will attempt to restore equilibrium, the lowest energy state.
Challenges in Vaporizor Design
One particular challenge in vaporizor design is distributing the heat equally throughout the cannabis. A vaporizor can transfer heat in a variety of ways such as convection, conduction, radiant heat or a combination, and each has challenges. Heating by conductive methods such as heating a metal bowl, has limited efficiency as the surface area of cannabis near the hot object is low. A significant temperature gradient (range) could contribute to wasted material (the cannabis near the bowl burns while the inner part is vaporized).
The design must target a mean temperature some percentage above the boiling point of the desired essential oils. The greatest efficiency is observed when the heat is thoroughly distributed with a stream of heated air, which penetrates the biomass, flows past all of the tiny surfaces, and maximizes vaporization.