What many of us “take for granted” in our daily lives, namely the heating, ventilation, air conditioning, and refrigeration systems, have a long and storied history that relies upon aspects of physics, engineering, and environmental considerations. That history is extensive, and beyond the scope of coverage here given the considerations of electromechanical discoveries and thermodynamics which have led to the compression cycle and other components of HVAC.  Given the variety of considerations in functions, however, each topic of H, V, A, and C will be considered separately:


Heating can be either “central” – via a furnace, pump, or boiler, whereby this heat centrally generated can be disseminated via convection, conduction, or radiation. Heat generation can be done via a variety of types – either using fuels of solid, liquid, or gas, or electricity (used to heat coils); subsequently, distribution is done via water (hydronics, which can also be used to heat water for bathing or other function) or steam via radiators. Air can similarly be used to either heat or cool, typically filtered via air cleaners to remove particles. Risks associated include possibility of by-product of incomplete combustion, e.g. carbon monoxide.


Defined as a means of “changing or replacing air in space to control temperature, moisture, odor, or remove microorganisms or other particulate matter, ventilation occurs both internal and external to a building; it can be divided into mechanical/forced or natural ventilation.

Controllable parameters include flow rate via direct drive fans (which incidentally can be used in cold weather from ceiling to floor, as heat rises and warmer air accumulates higher towards ceiling). Natural ventilation, relying upon windows used sometimes strategically (e.g. in warm weather with desired cooling, allowing outflow via high windows of warmer air and inflow via lower windows of cooler air to replace this escaped warm air, known as “stack effect”), Also, an important concept of air changes per hour is introduced – with normal being 4X/hour (or one air change per 15 minutes), with warehouses having perhaps only two; as an example of the other extreme, crowded nightclubs may have 30-50 air changes per hour, or one every 1-2 minutes. Positive pressure ventilation occurs when more air is supplied than exhausted, to keep out particulate matter; negative pressure does the opposite, keeping unintended internal matter from disseminating outdoors.

Air Conditioning

Air conditioning (AC) provides both cooling and humidity control – with fresh air intake about 10% (normally with an AC unit placed in a sealed open window). Refrigeration or AC rely upon removal of heat, achieved via radiation, convection, and/or conduction – with use of a refrigerant such as water, glycol mix, or a chemical, sent through a cycle which is pumped by a compressor at a high pressure and temperature, sent via heat exchanger which loses energy and heat to outside, returning to a liquid to an evaporating coil absorbing heat from indoors and returning to the compressor. Hence, by controlling its gaseous and pressurized state vs. allowing it to expand and in the process cool (and absorb heat), this cools a room depending upon the proper components being exposed to inside vs. outside; this may be reversed when heating vs. cooling is desired. More efficient systems may use a free cooling mode when outer air is cooler than needed inner cooling, so not requiring mechanical energy. Geothermal heat sources can be used in some cases for any of the functions, e.g. via water within the earth at a high temperature. Refrigerators work on a very similar idea, with added insulation to keep interior materials cool.


Use of present HVAC units will likely be amended to make the units more efficient – e.g. by changing fan blade angles, by considering how much wasted or inefficient function is involved and improving it, and by promoting certain regulation and standardization.

ISO building environmental standards have been developed (e.g. ISO 16813:2006) which provides HVAC considerations for noise, appearance, energy efficiency, sustainability, and evaluation of design.   Most HVAC engineers, members of the ASHRAE, are EPA-certified.

In Europe, the group named CIBSE provides guides for HVAC on a variety of topics, ranging from environmental design to sustainability, weather/solar/illuminance data, electricity in buildings, and maintenance.

As regulatory issues around “traditional” HVAC emerge, a new category for the future is also emerging – one which allows control of HVAC via the internet, remotely. Smartphone technology allows control via different apps (an upcoming topic under www.RavishonApps.com), which has recently been not only the subject of convenience, but concerns over security (as others could take control and cause problems ranging from high monthly bills to potential damage). The topic of HVAC itself is very broad, and so will its future be – essentially “climate control” relies upon HVAC, whether in our homes, offices, hotels, stores, cars, or even airplanes (or the Space Station, for that matter)… it is, in a word, often essential to life itself.


(Information above has been acquired from numerous sources, including www.kudzu.com, www.howstuffworks.com, www.wikipedia.org, and www.constructionknowledge.net, among others)

Global Warming

History of Global Warming Discovery

Few topics simultaneously involve the North Pole, accusations of imaginary made-up ideas, and the naughty-vs.-nice argument. Beyond Santa Claus, global warming is one such category – with ice caps melting in the North Pole, partisan debate politically present with fervor about whether the phenomenon actually exists (and whether it is being contributed to by our factories/carbon emissions/etc. – i.e. through mankind’s irresponsibility).

Historically, for about 2000 years before 1850 (the mass industrialization age, presumably), temperatures had been relatively constant. However, since then, and particularly since 1906, temperatures have been increasing slightly but significantly – with an approximately 0.13-0.22 degrees C increase since 1979 per decade, which cumulatively has led to a 0.74 degree C mean increase over approximately the last 100 years. In terms of energy “balance,” the energy leaving earth has been less than energy entering earth – hence, there is been warming. While land temperatures have increased twice as fast as ocean temperatures (due to ocean heat capacity), average Arctic temperatures have been increasing at almost twice the rate of the remaining world in 100 years.

The idea of greenhouse gases causing a “greenhouse effect” was proposed in 1824 by Fourier, and developed carefully based upon practical measurements into a model by Callendar in the mid 1900s. To understand what this means, consider that earth’s naturally occurring greenhouse gases cause a warming effect of 33 deg C (or 59 deg F) – without these, the earth’s temperature would normally be below freezing. Actual gases such as water vapor (about 60%), carbon dioxide (about 20%), methane (about 7%), and ozone (about 5%) contribute to this warming predominantly among such gases. Interestingly, since 1750, the concentration of carbon dioxide has increased by 36% and methane has increased by 148%. For those arguing that “this may just be cyclical,” supporters of global warming due to industry offer that these levels are much higher than in the last 800,000 years on earth (though higher values on earth were noted about 20 million years ago). Among components causing such increase, fossil fuel use (coal burning for 43%; oil 34%; gas 18%; and cement 5%, with gas flaring less than 1%).


Present-Day Global Warming

Perhaps equally interesting (and contrary to how the argument is often phrased), the ozone depletion is not necessarily related to global warming – in fact, there is evidence to some extent that ozone depletion in the stratosphere may lead to regional global cooling.

Also interestingly, whether by particulate matter from volcanoes or from human-caused industry by-products, a cooling effect has been noted from sunlight deflection from such particles.

By using satellite data from orbit around the earth, the amount of sun energy can be measured (hence excluding the sun’s energy increase as a source of global warming, as this has appeared relatively constant during this time period).

Based upon trends and such data, predictions for what may be expected include a rise in sea level of about 1-4 meters by mid-21st century by some estimates – this could, in turn, result in massive flooding. In the case of some islands, such as the Maldives, complete submersion of many key islands could occur. Landmasses with large ice components, such as Greenland, could be reduced to a fraction of their present sizes.


Future Global Warming Concerns

One of the plaguing questions is: so what do we need to do for the future, if global warming is happening to the detriment of the future?   An initial step involves understanding both what such implications would involve, what is potentially causing such issues, and what we need to do to intervene.

Food production could be adversely threatened due to water from crops either being too great or not adequate, hence causing a mismatch – this, in turn, would affect human life, which may depend upon crop production.

So how should this be solved? In general, three responses have been proposed: (1) intervention to lessen the blow; (2) adjustment of lifestyle to accommodate such climate change; (3) engineering the climate to suit a more favorable result (beyond what would be done as simply intervention to lessen the blow). Among these, (1) involves the reduction of greenhouse gases by reducing carbon emissions – namely carbon dioxide and methane, as possible, via altered manufacturing processes leading to fewer such gases, planting greater trees and avoiding deforestation, and similar methods. (2) would involve accepting climate change, and adapting – e.g. changing locations of crop growing, preparing for floods pre-emptively, etc. Item (3) above, purposefully altering carbon dioxide, for example, may have many unintended side effects which may not be readily perceivable presently, and has been largely rejected as a method to presently try.

To balance out the argument, there are naysayers who will point to the “absent heating period from 1998-2012, with only 0.04 deg C increase vs. 0.21 in the past decade” post-El Niño, which occurred after severe climate changes in many parts of the world

Ultimately, a combination of (1) intervention in our present contributions to global warming (part of which has been done in certain areas – contrast Los Angeles to Beijing); and (2) adaptation to pre-emptively help reduce effects of flooding and improve potential future agricultural practices would likely help the most, with this recognized and potentially reversible (or at least minimize-able) problem. Ideas such as a “carbon tax” have been proposed to tie in financial and social measures. Such responsibility, and its political, legal, and life-related implications, should be recognized and addressed, before the effect is not so easily reversible or even containable.


(Information above has been acquired from numerous sources, including www.iivescience.com, www.globalwarming.org, www.wikipedia.org, and www.nature.com, among others)

Mining: The Cobalt Example

Mining History

Egypt, China, and eventually Europe used cobalt.  Coined from “kobold” by Germans (for “goblin”), it was officially described by Swedish chemist Brandt in 1735, and in 1938 Livingood & Seaborg discovered Cobalt-60 isotope (“Co”), used famously at Columbia University in the 1950s to show “parity violation in radiaocative beta decay.”

With cobalt mines shifting in the 1800s from Scandanavia to New Caledonia, to Ontario/Canada, to Katanga Province (Congo), shortages were rare despite conflicts in the Congo (as much Cobalt could be recycled or substituted by another material).  U.S. reserves found near Blackbird Canyon/Idaho led to the firm “Calera Mining Company” being started.  It is important to remember that Co is often found as a by-product of Nickel & Copper mining activity.

Katanga in Congo remains the source of around 40% of the world’s Cobalt, and CAMEC (Central African Mining & Exploration Company) affiliated with Zhejiang Galico Cobalt & nickel Materials of China as a supplier in 2008.  Through mainly chemical reactions, Cobalt is separated from ore components, and is used mainly in metal superalloys which confer incredible temperature stability (allowing use in gas turbines, jet aircraft – though not as strong as nickel alloys).  Cobalt is used with titanium in medicine, for orthopedic implants.  Other alloys (like chromium, tungsten, molybdenum) are used in implants.  For dental implants, cobalt can substitute for patients who suffer from nickel allergy.  Other alloys (Al-Ni-Co, or Alnico), and Samarium-Cobalt permanent magnets, as well as platinum-Co jewelry, also exist.  Cobalt oxide with intercalated Lithium (LiCoO2) with Li set free during discharge between CoO2 layers, as well as use in Nickel doing the same (NiMH, or Nickel metal hydride) are useful in batteries.  Other uses in chemical reactions are noted for cobalt.

Smalt, a blue-colored glass, is made by combining the roasted mineral smaltite, quartz, and potassium carbonate.  Cobalt green and cobalt blue use followed (especially in paintings).

Mining, or removal of geological materials from earth (via ore body, vein/coal seam), can be done for base metals, precious metals, coal, diamonds, limestone, non-renewable resources such as petroleum, natural gas, or water.  Dating to pre-historic times for fashioning weapons, the oldest known mines are reportedly “Lion Cave” in Swaziland, Africa (hematite for red pigment), Egyptians for green malachite stones, and then Athens and Rome.  Romans developed “hushing” – building a reservoir to flood the “overburden” to expose bedrock and gold veins, then fire-setting to heat the rock to “shock” it and

Such methods were undertaken in Spain and England (for gold, silver, tin, or lead, for example).  Using “adits” driven through barren rocks, the mining areas were ventilated for fire-setting, using reverse overshot water-wheels (on a treadmill based operation), for copper and other metals.

In the middle ages, mining for copper and iron ore for weapons/armor (upto 100 lbs per knight) with introduction of “black powder” for blasting, via Hungary.  Processing was done by arrastra, like threshing grain;

In North America, native Americans mined copper about 5000 years ago, for weapons and tools; quartz mines also existed.  Copper, gold, and turquoise were mined as well, with gold preferable as it did not require smelting (i.e. the process of removing other mixed-in or bound substances, by heating, chemical reaction, or both, as for example CO is used to take away oxygen to form CO2).

While conditions have improved somewhat, significant peril still is present in the mining industry today.


Often, the initial process involves a feasibility study (e.g. to determine presence of the enrichment factor of ore) regarding whether the project should proceed.  Surface mining, used for over 85% of metals and ores, accesses either placer (within loose material) or lode (within hard rock, e.g. within a vein) material.  Recovery techniques are then used.

Rarer mining, such as uranium mining, are done using a solvent.  Strip mining (taking off strips) or mountaintop mining (for coal, usually) is also done.  Sub-surface mining (drift – horizontal; slope – diagonal; and shaft – vertical) in hard and soft rock are used.  Room and pillar mining (with destruction of pillars, allowing the room to cave in, loosening more metal) offers other techniques.

Environmental erosion may occur in combination with sinkholes (sometimes in combination with logging, to help store debris from mining).  Based upon self-policing and other institutions, regulations are enforced to help minimize environmental deterioration.

A large amount of waste (e.g. 99 tons of waste per 1 ton of copper mined – with a higher ratio for gold mining (!)) results, known as “tailings” – these can be toxic, are contained in ponds with dams, and can occasionally cause a disaster and empty into local rivers or other water sources.  Though submarine tailing emptying has been proposed by mining industry as “ideal” it is banned in U.S. & Canada, but allowed in developing nations.

Banks have also been significantly involved since 1955 in mining, as exemplified by the World Bank’s provision of over $2B; also, privatization has been encouraged for national mines, with some regulations (which have fallen short in some cases, per opinions).  Regulations in smaller countries, with “artisanal” mines where transparency may not be as good, are difficult to monitor.

Industrial mining capitals globally involve London (Rio Tinto, BHP Billiton, Angio American PLC), US (coal and non-metal minerals).  Of the global market cap of 50 trillion (USD), US compares at 962B.  Due to large CapEx, most mining is done by multi-national, large teams.  Exploration is carried out by smaller groups such as individuals or mineral resource companies called “juniors” backed by VCs, and actual mining companies (larger companies).  Countries interested in mining (e.g. Canada) have special stock exchanges focusing upon funding mining activity.

Two classification schemes for mining operations can exist – (1) by category — oil & gas/coal/metal ore/nonmetallic mineral mining & quarrying/support services for mining.  Seismic prospecting and remote-sensing satellites are techniques used to help exploration, particularly with oil & gas; (2) by size – major (Rev > 500m USD); intermediate (50mm – 500mm); and junior (equity-financed, mainly exploration, <50mm).

Interestingly, copper forms the basis of many statues – including the Statue of Liberty. One of the other more striking examples is the large statue amidst the hills of Buddha, which is located near Hong Kong airport.

Mining Cobalt for The Brain: A Special Case Study

Cobalt is found naturally only in a chemical combination with other elements, with the pure (free) element produced by smelting (reduction, interestingly giving off Arsenic, a poisonous vapor) and appearing as a hard, shiny, sliver-gray metal.  Discovered in 1735, Cobalt-rich areas include “copper belt regions” of the Congo & Zambia.  Cobalt is used in alloys, blue glass/ceramics/paints/etc. coloring, and Cobalt-60 is used as an isotope radioactive tracer to produce gamma rays (e.g. in Gamma knife radiosurgery).  It occurs in co-enzymes (cobalamins, e.g. Vit B12), and is a essential trace mineral for animals, bacteria, and fungi.

Cobalt can exist as different types: oxides (green, brown, blue), halides (pink, blue, green, blue-black, & red for hydrated), and enantiomers (optical isomers) which give crystals.  Cobalt-59 is the only stable isotope in nature, but Cobalt-60 has a half-life little over 5 years.

Radioisotopes:  Cobalt-60 use as a gamma ray source (when bombarded by neutrons) has been used for external beam radiotherapy/Gamma Knife, cold pasteurization, and radiography (with discarding needing to be done very carefully, due to the extreme cobalt dust toxicity).  It is also used in the Schilling test (for B12 deficiency, intrinsic factor (?)).  Interestingly, its lack can cause “bush sickness” in ruminants (e.g. cows), cured by adding Co to fertilizer, but for non-ruminants, they rely upon digesting feces (as bacteria must produce the Vitamin B12, as Cobalt cannot directly be absorbed and converted by these animals).  At higher levels, cobalt can be poisonous.

The goal of Cobalt as a gamma generator for the Gamma Knife, for example, is that multiple particles converge on a central target (e.g. a brain tumor) with minimal damage to the surrounding brain.  Hence, the implications of cobalt mining are significant – even involving the human brain!  In A Gamma Knife, for example, 201 “beams” using Cobalt as a source converge upon a focused region of target tissue, minimizing radiation to the surrounding brain (similar to placement of a hand between the magnifying glass under direct sunlight and the ground, where the hand does not become burned but the paper below where the rays focus may).

Special handling considerations must be employed for Cobalt – its use is indeed unique due to its radioactive properties; hence it remains essential to be able to aid many today.

(Information contained here was acquired from multiple sources, including discussions, reading, and websites such as pwc.com, miningindustryreview.com, and/or Wikipedia.org)