Keeping it Cool

We humans are unique in so many ways, but perhaps our mastery of the systems used in getting food into our mouths is the most remarkable. From our humble hunter-gatherer beginnings, in which we behaved much as any other animals, we have discovered agriculture, domesticated animals, learned to harvest milk and eggs and are nowadays even capable of growing a steak from just a few cells (we’ll temporarily gloss over the cost and taste of the finished product). However, arguably just as important as these advancements has been our ability to store food, allowing us to survive the harshest of winters and conditions in numbers few other animals could hope to match.

Our methods of food storage have varied widely over the years; beyond the simple tactic of ‘keep your food somewhere basically dry and clean’, in the last few decades we’ve moved on from our old favourites to explore as wide a variety of solutions as chemical preservatives and freeze drying. However, today I wish to explore an older, yet arguably far more interesting, method that remains our current favourite method of home food preservation: that of refrigeration.

Refrigeration, or the highly technical art of ‘making food colder so bad things can’t survive’, is an ancient idea; ice houses have been found in Iran dating from 1700BC, and were in use in both China and the Roman Empire throughout both culture’s long histories. Since making their own ice was impossible using the technology of the time, these ancient civilisations simply moved existing ice to a designated place where it with useful and came up with ingenious ways to make sure it stayed cold throughout the long summers; these great buildings would have immensely thick walls and were then packed with straw or sawdust to prevent the air circulating, thus helping to maintain their temperature. Thanks to their thick walls, ice houses were necessarily vast structures, acting rather like communal refrigerators for a local lord and his community and capable of holding up to thirty thousand tons of food.

In other countries, where snow and ice was harder to reliably come by (even in winter), refrigeration didn’t really catch on and people stuck with salting their food. However, because this a) made a lot of food taste disgusting and b) meant you still had to drink warm beer, by the seventeenth century it became relatively common for the rich across Europe to import ice (at vast expense) to their own personal ice houses, allowing them to serve fancy drinks at parties and the like and enjoy an unsalted pork roast in February. Ice was a symbol of luxury and status, which is presumably one of the reasons why ice sculptures are even today considered the pinnacle of class and fine living (that and the fact that they’re really, really cool). During the Georgian and Victorian eras, it was common practice for families going out for a day’s jolly (particularly in the colonies) to take an ice box of food with them, and there were even ice shops where the rich would go to buy high-quality, exceptionally clear ice for whatever party they happened to be hosting- but, by the end of the century that business would be long bust.

Y’see, in 1805 a man named Oliver Evans, who would later become known as ‘the father of refrigeration’, invented a device called the vapour-compression refrigeration machine. This is, basically, a series of tubes containing a stable coolant; the coolant is first compressed, then condenses (causing it to lose the heat it’s picked up- this is the vapour-compression bit), before going back inside and evaporating again thanks to a mixture of a pressure change and temperature change, thus allowing it to pick up heat. This rather convoluted evaporation/condensation procedure (first investigated by Benjamin Franklin and a chemistry professor called John Hadley half a century earlier) wasn’t actually the preferred solution for a few decades, since the earliest devices built were ‘compression-compression’ systems that used air as a coolant and were thus only able to change its pressure rather than get it to liquefy. Regardless, it was soon realised the vapour-compression system allows a device to more efficiently control the transfer of heat from in to out rather than vice versa, and is now pretty much universally used in modern day ‘heat pumps’ of all sorts.. Incidentally, heat pumps are among the most efficient systems ever devised for heating/cooling a space, and nowadays they are increasingly used (in the opposite direction, of course), to heat houses, as they use far less energy than conventional methods of heating.

But anyway; back to fridges. Evans’ design never actually built a prototype of his design, but it was picked up on and revised several times over the next seventy-odd years until the design was sufficiently advanced to be used in commercial ice makers, putting the old ice ‘manufacturers’ (who simply got their ice out of a convenient mountain lake or glacier) out of business, and by the early 20th century the devices got so good that they were able to liquefy air.

Surprisingly, it wasn’t until after this point that the modern science of refrigeration began to make it into our homes. It took until 1913 for a patent to be issued for a domestic refrigerator, and even that was just a way of keeping an existing ice box cool; it didn’t actually cool the interior of the fridge down. However, the following year the USA got the awesomely-named Kelvinator refrigerator, the first properly practical domestic fridge that held some 80% of the market by 1923. During the economic boom of the 1920s, fridges were among the many devices whose popularity exploded, and they gradually became bigger, sleeker, more practical and more efficient in the process. By the 1930s they’d even managed to find a coolant that wasn’t highly corrosive or toxic, which all seemed terribly fantastic in the days before most people knew what ‘CFCs’ and ‘the ozone layer’ were. By 1940 the idea of attaching a freezer (at a sub-zero temperature) to one’s fridge (which usually operates at about 3ºC) became commonplace, and since then most of the advancements in the field of domestic refrigeration have been limited to making fridges bigger, easier to clean (particularly with the introduction of injection-moulded plastic components), more energy-efficient and more of a middle-class fashion statement.

However, this does not mean that the science of refrigeration is slowing down: recently, a British company called Reaction Engines Ltd. demonstrated their prototype air-breathing rocket engine, whose key feature was a revolutionary new type of heat exchanger. Despite a design utilising pretty much exactly the same science you’d find at the back of your fridge at home, this heat exchange is capable of dropping the temperature of air from several hundred degrees to -150ºC; in a hundredth of a second. That change in heat energy represents roughly the power output of a medium sized power station from a device that weighs significantly less than a hatchback. I would love to explain all the mechanics of this technology to you, but right now I wish for little more than to sit back and marvel.


The Slightly Chubby Brigade

As the news will tell you at every single available opportunity, we are living through an obesity crisis. Across the western world (USA being the worst and Britain coming in second) our average national BMI is increasing and the number of obese and overweight people, and children especially, looks to be soaring across the board. Only the other day I saw a statistic that said nearly a third of children are now leaving primary school (ie one third of eleven year-olds) overweight, and such solemn numbers frequently make headlines.

This is a huge issue, encompassing several different issues and topics that I will attempt to consider over my next few posts (yeah, ‘nother multi-parter coming up), but for many of us it seems hideously exaggerated. I mean yes, we’ve all seen the kind of super-flabby people, the kind the news footage always cuts to when we hear some obesity health scare, the kind who are wider than they are tall and need a mobility scooter just to get around most of the time. We look at these pictures and we tut, and we might consider our own shape- but we’re basically fine, aren’t we. Sure, there’s a bit of a belly showing, but that’s normal- a good energy store and piece of insulation, in fact, and we would like to have a life beyond the weight-obsessed calorie counters that hardcore slimmers all seem to be. We don’t need to worry, do we?

Well, according to the numbers, actually we do. The average height of a Briton… actually, if you’re stumbling across this at home and you consider yourself normal, go and weigh yourself and, if you can, measure your height as well. Write those numbers down, and now continue reading. The average height of a Briton at the moment is 1.75m, or around 5’9″ in old money, and we might consider a normal weight for that height to be around 80 kilos, or 170 pounds. That might seem normal enough; a bit of a paunch, but able to get around and walk, and certainly no one would call you fat. Except perhaps your doctor, because according to the BMI chart I’ve got pulled up a 5 foot 9, 80 kilo human is deemed clinically overweight. Not by much, but you’d still weigh more than is healthy- in fact, one stat I heard a while ago puts the average Briton at this BMI. Try it with your measurements; BMI charts are freely available over the web.

This, to me, is one of the real underlying causes of ‘the obesity epidemic’- a fundamental misunderstanding of what ‘overweight’ consists of. Whenever our hideously awful everyone-dead-from-McDonalds-overdose etc. etc. diet is brought up on the news, it is always annotated by pictures of hanging bellies and bouncing flab, the kind of bodies that make one almost physically sick to look at. But, whilst these people certainly exist, there are not enough of them for the obesity issue to be even worth mentioning in everyday society; whilst the proportion of morbidly obese people is significant, it’s not seriously worth thought for most of us.

No, the real cause for all the chilling statistics we hear on the news is all the people who don’t look to be overweight. The kind whose diet isn’t appalling (no 24/7 McDonaldses), who are quite capable of exercise when it suits them, and who might take a rough glance at the dietary information of the stuff they buy in the supermarket. But these people are nonetheless hovering on the overweight borderline, pulling up the national average, despite the fact that they don’t consider anything to be wrong; in fact, some women who are according to the evil numbers overweight, may consider it almost dutiful to not become obsessed over shedding every pound and to maintain their curves. Having a bit of excess weight is, after all, still better than being underweight and anorexic, and the body image pressures some young women are coming under are just as much of an issue as national obesity. Even for those who don’t have such opinions, many of the slightly overweight feel that they don’t have any weight issues and that there’s surely no significant health risk associated with a ‘bit of meat on your bones’ (it’s actually muscle, rather than fat, that technically forms meat, but ho hum); as such, they have absolutely no motivation to get their weight down, as they don’t think they need to.

I won’t waste much of my time on all the reasons for this statement, but unfortunately even this slight degree of overweight-ness will significantly increase your risk of major health problems somewhere down the line, particularly that of heart disease (which is going through the roof at the moment); diabetes isn’t likely to be a risk for the overweight unless they’re really overdoing things, but that’s also a potential, and very serious, health hazard. The trouble is that many of us find it hard to make this connection if we basically feel healthy. Despite what the doctor says and no matter how much we trust them, if we are capable of going for a nice walk and generally getting about without getting out of breath or feeling bad then we probably feel justified in thinking of ourselves as healthy. Our heart doesn’t seem about to give out, so why worry about it.

The thing to remember is that the heart is just a muscle, so if it isn’t stressed it will degrade just like any other. You know those triceps that haven’t done a press up in five years? Feel how small and weak they are? Yeah, that kind of thing can quite easily happen to the muscles that are responsible for keeping you alive. Your heart might be pumping all day long and be a different type of muscle, so the process will be slower, but give it twenty years and you might start to see the effects.

But anyway, I’m not here to lecture you about your health; that’s far too depressing and dull for my liking- the only point I was trying to make is that many of the accidental contributors to ‘the obesity epidemic’ are probably unaware that their health is in any way a problem, and not really through fault of their own. So whose fault is it then? Well, that one can wait until next time…