Heat transfer tubes and refrigerator: what they have in common

1. Step 1. Heat transfer tubes — is part of — Solar water heater. They carry away heat.
2. Step 2. Solar water heater — is a kind of — Water heater. A solar water heater is a boiler warmed by the sun.
3. Step 3. Water heater — has part — Thermostat. A thermostat.
4. Step 4. Thermostat — is part of — Refrigerator. A thermostat.

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