Bench Degree·REFRIGERATIONchapter
Appendix A: The Bench
The whole volume’s kit in one place. Every experiment in this book is on this list, so you should never have to stop mid-chapter and wait two days for a delivery. Each chapter names what it needs when it needs it and points back here; if you would rather order once and be done, order from this list.
This book asks you to measure things at nearly every step. That only works if the equipment is already on the bench when you reach the paragraph that needs it, so here is the whole volume’s requirement in one place.
Nothing here is specified by brand or by part number. Every item is described by dimension, range or grade, so the list stays orderable from anyone, anywhere, for as long as the book exists. Suppliers change, product listings get relisted under new numbers, and a printed link dies permanently. A specification does not.
Three things to know before you spend anything.
You do not need all of it to start. Section 1 is enough for Chapters 1 through 7, which is a third of the book, and it costs about fifty dollars. Buy that, get going, and come back.
You probably own more of this than you think. The bicycle pump, the kitchen thermometer, the box fan and the multimeter are already in a great many houses.
Two items are worth more than they cost. A decent multimeter and an infrared thermometer will outlive this book and change how you look at every machine in your house. If the budget is tight, spend it there.
Section 1: The starter set, for Chapters 1 to 7
| Item | Specification | Rough cost |
|---|---|---|
| Bicycle pump | Any hand or floor pump with a metal barrel. A metal barrel matters, because you need to feel it get hot. | owned, or $20 |
| Compressed air duster | One can, the kind sold for cleaning keyboards. Check the label says difluoroethane or tetrafluoroethane. | $6 |
| Digital thermometer | Two of them, ideally. Range at least minus 20 to 120 °C (minus 4 to 250 °F), resolution 0.1 degrees. Probe type, not forehead type. | $12 each |
| Infrared thermometer | Non-contact, range at least minus 30 to 300 °C (minus 22 to 570 °F). Cheap ones are fine for comparisons. | $25 |
| Hand vacuum pump | Automotive brake bleeder type, with a gauge reading down to at least 25 in Hg (about 85 kPa below atmosphere). | $25 |
| Vacuum-rated jar or chamber | A small chamber, or a jar with a sealed lid fitting. Must be rated for vacuum; a decorative jar can implode. | $15 |
| Unglazed terracotta pot | Small plant pot, 100 to 150 mm (4 to 6 in), drainage hole pluggable. Plus one glazed or plastic pot the same size, for comparison. | $10 |
| Glazed pot, same size | For the comparison in Chapter 2. | $5 |
| Cotton shoelace or gauze strip | For the wet bulb. Any absorbent cotton. | owned |
| Small fan | Any desk or box fan with at least two speeds. | owned, or $20 |
| Kitchen scale | Range to 2 kg (5 lb), resolution 1 g (0.04 oz). | $15 |
| Syringe, 20 mL or larger | Needle removed, tip cappable. For Cullen’s 1755 experiment. | $3 |
| Isopropyl alcohol | 90 percent or higher. | $6 |
| Notebook and graph paper | Several experiments ask you to plot readings against time. Do it on paper; the shape is the point. | $5 |
Starter set total: roughly $150, or about $90 if you already own a pump, a fan and a kitchen thermometer.
Section 2: Added for Chapters 8 to 15, the measurement chapters
| Item | Specification | Rough cost |
|---|---|---|
| Refrigeration gauge manifold | Two-valve or four-valve set with hoses. Must match the refrigerant you will meet: R-410A uses different fittings from R-22, so buy for R-410A unless you have a specific older machine. | $60 to $140 |
| Clamp meter | AC current, jaw opening at least 20 mm (0.8 in), range to 100 A. Reads current without breaking the circuit. | $40 |
| Pipe clamp thermocouple | Straps to a copper line to read line temperature. Two of them is better, because superheat and subcooling want both ends at once. | $20 each |
| Anemometer | Vane or hot-wire, reading to at least 10 m/s (2,000 ft/min). For airflow across a coil. | $35 |
| Sling psychrometer, or two thermometers and a shoelace | You can buy one or build one. Building one teaches more. | $0 to $40 |
| Pressure-temperature chart | For your refrigerant. Free from any manufacturer. Print it and keep it in the notebook. | free |
A note on the gauge manifold. Attaching gauges to a working system is the moment this book stops being theoretical. It is also the moment you can do damage. Chapter 12 covers it properly, including the fact that in most jurisdictions it is illegal to deliberately release refrigerant to atmosphere, and that connecting and disconnecting hoses loses a small amount every time. Practise on a scrap window unit before you touch anything you rely on.
Section 3: The build, Chapter 11
| Item | Specification | Rough cost |
|---|---|---|
| Thermoelectric module | Peltier type, 40 x 40 mm (1.6 x 1.6 in), 12 V, 60 W class. | $10 |
| CPU heatsink and fan | Any scrap tower cooler with a 12 V fan. | scrap, or $12 |
| Bench power supply or 12 V adapter | At least 5 A at 12 V. | $20 |
| Insulated box | Any small cooler box, or rigid foam board and tape. | $10 |
| Thermal paste | Any. A small tube lasts forever. | $6 |
What is deliberately not on this list. A working vapour-compression build needs brazing equipment, a vacuum pump capable of pulling to 500 microns, a micron gauge, a recovery machine, and in the United States an EPA Section 608 certification to purchase refrigerant at all. That is a real workshop, not a bench, and Chapter 11 says so rather than pretending otherwise. The thermoelectric build teaches heat pumping honestly and safely, and it is the one this book asks you to make.
Section 4: Free, and worth more than most of the above
Several of the best experiments in this book cost nothing because they use machines you already own.
- Your refrigerator. Chapter 1 has you feel the condenser coils and find the heat that used to be in your milk. Chapter 10 has you find the metering device by following a temperature drop with a bare hand.
- A scrap window air conditioner. Free from a kerbside, a recycling centre or a neighbour. Chapter 17 takes one completely apart. Get one early. It is the single most useful object in this book and the supply is seasonal.
- A propane or three-way absorption refrigerator, in any caravan, camper van or hotel minibar. Chapter 3 asks only that you look at one and notice it makes cold with no moving parts.
- Any heat pump. Chapter 19 asks you to watch one run a defrost cycle, which is the strangest thing a heating machine ever does.
- Your own house. Chapter 14 has you measure wet bulb and dry bulb in four rooms, and Chapter 15 has you calculate the cooling load of one of them.
Section 6: Kits
A single collection covering everything above, ordered once, is the obvious convenience and it is being worked on. When it exists it will be at benchdegree.com/kit/refrigeration, and that address is deliberately the only place it will be published: suppliers and product listings change, and a link printed in a book cannot be corrected. The specifications in this chapter can be taken to any supplier and will still make sense in twenty years.
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