Sheep and New Zealand go together like Marmite and cheese, bangers and mash, $10 bottles of wine and a fresher Byo.
Striking up a yarn with a visitor to New Zealand, about New Zealand, the conversation at some point, will head towards how famous our little collection of islands are for sheep.
‘New Zealand is famous for sheep, isn’t it?’
Luckily the Lord of the Rings franchise came along, otherwise we would still only be famous for our large (but decreasing) sheep population.And for many, the humble sheep symbolise New Zealand as a nation.
But do you know why? And no, it’s not because our men are lonely.
Sheep farming was established in the 1850s’ and were only farmed for their wool. For many decades’ wool accounted for more than a third of New Zealand’s exports by value.
Now, at this time a suave young chap by the name of William Soltau Davidson enters our history.
He arrived into Port Chalmers on the 30 December 1865 and went straight into his career as a Shepard. He eventually acquired some land and begun conducting experiments with his mate James Little, to cross breed Merinos with Lincoln Stud rams resulting in the now famous New Zealand breed, the Corridale.
We, as a country, did such a good job at farming sheep for wool that the overseas markets almost collapsed, resulting in an oversupply which outpaced demand.
Pat yourself on your back New Zealand, top of the class! We shot ourselves in the foot.
This resulted in wool prices dropping by a third between 1873 and 1888.
During this time, ole’ willy became the general manager of the New Zealand and Australian Land Company in 1878 and became increasingly aware of the slump in the wool industry that we relied on so heavily. He wanted to find another use for sheep other than wool (and companionship).
Export canned meat! That’s an answer, surely!
Mmmmmm how appetising does canned sheep tongues or curried rabbit sound!!!
New Zealand tried to crack into the canned meat market but it didn’t quite sit well with the Europeans, it was however, extremely popular in the south pacific, which still carries on today! (All Hail Bully Beef!)
The result was refrigeration. Nothing on a large scale had been attempted before, the Aussies tried but like many things, they failed miserably. While based in the United Kingdom, Willy researched different methods of refrigeration till the cows (and sheep) came home, finally settling for a coal-powered Bell Coleman Freezing plant. His plan was to fit out the passenger sailing ship, the Albion Line’s Dunedin with the freezing plant. This little gem could cool the entire hold to 22°C below the outside temperature.
Blah, Blah, Blah, this blog is meant to be about science not a dam history lesson!!!!
Yeah and I’m getting there!
Now remember this is during the late 1800’s, nothing was easy. Most of the first cargo originated from Brydone’s slaughterhouse at Totara Estate, near Oamaru, then transported by rail to Port Chalmers in iceboxes.
The whole ordeal of freezing the sheep and mutton carcasses, once they arrived at Port Chalmers, was done on board the Dunedin. This meant that while the Dunedin was docked at Port Chalmers, sheep carcasses were frozen using air cycle machines (the Bell-Coleman) which blew the cold air stream directly over them. About 300 carcasses could be frozen at once, while in just over two months, the Bell-Coleman plant on board froze nearly 10,000 carcasses.
Just under 5000 carcasses had their overseas adventure, setting sail on 15 February 1882. The rest were destined for dinner plates around New Zealand or storage.
Now this is where we get Sciency!
How does refrigeration work?
The Bell-Coleman plant (and cycle) is named after John Bell and Joseph James Coleman (duh), who had been involved in American chilled beef shipments and who patented the design of the compression refrigeration machine. The process focused upon the use of compressed air for its chilling effects. The effect, which also led to the development of air-conditioning, is known as the Bell-Coleman effect or Bell-Coleman Cycle, or more commonly known as the gas refrigeration cycle.
For the purpose of this little write up, I will explain the science behind the refrigeration cycle.
Basically, this happens:
It moves heat.
Easy aye? Yeah na!
If it was that simple, this blog would be done and i’d be in bed!
There are two (of the three) thermodynamic laws that are significant to understand the basic refrigeration cycle:
The first law of thermodynamics explains that energy cannot be neither created nor destroyed, but can be changed from one form to another.
The second law of thermodynamics explains that entropy of any isolated system always increases.
Entropy in an isolated system (say, like a closed refrigerated system) that is not in equilibrium will tend to increase over time until it reaches a maximum equilibrium level.
For example: If you keep the door open between two adjoining rooms of different temperatures the cooler room will become warmer and the warmer room will cool down until they both reach the same final temperature.
The refrigeration cycle is a process that simply removes heat from an area that is not wanted and transfers that heat to an area that makes no difference. Therefore, going back to our historic Bell-Coleman freezing machine, it did not create heat, it just transferred it.
For heat to transfer, there must be a temperature and pressure difference. The refrigeration system removes heat from an area that is low-pressure, low temperature (evaporator) into an area of high-pressure, high temperature (condenser).
Here’s a bullet point explanation, complete with GIF:
- Air is taken into the compressor from the atmosphere and compressed (in this case by a steam powered compressor).
- The hot compressed air is cooled in heat exchanger up to the atmospheric temperature (in ideal conditions).
- The cooled air is then expanded in an expander, the resulting air temperature is below the atmospheric temperature due to isentropic pressure.
- The low temperature air coming out from the expander enters the evaporator and absorbs the heat.
- The cycle is repeated.
Basically, this is what occurred on the Dunedin. This is how this pioneering use of technology transformed New Zealand’s economy. Sheep were no longer grown solely for wool, and the wealth of the nation developed rapidly. On 15 February 1882, the Dunedin sailed with 4331 mutton, 598 lamb and 22 pig carcasses, 250 kegs of butter, hare, pheasant, turkey, chicken and 2226 sheep tongues, and arrived in London 98 days.
More than a single successful shipment was needed to create a new industry. Old Willy Davidson set to work creating a marketing and insurance structure to underpin refrigerated shipping. Within five years, 172 shipments of frozen meat were sent from New Zealand to the United Kingdom, of which only 9 had significant amounts of meat condemned. The Dunedin completed nine more voyages until her loss in 1890. The new technology ultimately enabled the owner-operated (family) farm to become the standard economic unit in rural New Zealand for the next century.
If you have 19 mins, love a drab, monotone voice and the idea of refrigeration excites you, then this clip is for you:
(Recommended listening to it at x 1.25 speed)
But if you value your time on this earth this gives a good overview:
And the rest, as they say, is history! New Zealand became the world leaders in refrigerated meat products, which we dominated the crap out of for many decades… it also opened up our country to being the but of many ‘sheep loving’ jokes.
I hope you enjoyed this journey into the world of refrigeration. Next time you are hoeing into a juicy piece of lamb, smothered in mint sauce, I hope you will appreciate the journey its forebears went through so you could eat world class New Zealand lamb!
Until next time!
Images and Gif’s sourced under the creative commons license.
Fipenz, A. C. (2009). Refrigeration: underpinning the New Zealand economy for over 125 years. Institution of Professional Engineers New Zealand.
Price, S. H. (2007). Vapor-Compression Refrigeration (Conventional Refrigeration