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Thermal expansion in hot water systems: This article defines thermal expansion in water equipment in response to temperature, and explains the concomitant increase in system pressure. We show how to calculate hot water pressure increase in water heaters and boilers as a function of the increase in water temperature.
Heated Water Expansion Chart. Expansion tanks provide an air cushion into which the boiler water can expand when boiler water is heated. Based upon an initial water temperature of 40¡F. Water Temperature.
When water is heated, it expands. For example, water heated from 90oF (32oC) to a thermostat setting of 140oF (60oC) in a 40 gallon hot water heater will expand by almost one-half gallon.
The approach temperature is the smallest temperature difference between the primary and secondary fluids at any point within a heat exchanger. For a counter flow or cross flow plate heat exchanger it will usually be the difference between the primary flow temperature and the secondary flow temperature. For space heating applications an approach
Table A–1 Molar mass, gas constant, and critical-point properties Table A–2 Ideal-gas specific heats of various common gases Table A–3 Properties of common liquids, solids, and foods Table A–4 Saturated water—Temperature table Table A–5 Saturated water—Pressure table Table A–6 Superheated water Table A–7 Compressed liquid water Table A–8 Saturated ice–water vapor
Tables B-1 and B-2 present data for saturated liquid and saturated vapor. Table B-1 is presented information at regular intervals of temperature while Table B-2 is presented at regular intervals of pressure. Table B-3 presents data for superheated vapor over a matrix of temperatures and pressures.
What is Thermal Expansion? When water is heated it expands. For example, water heated from 90oF to a thermostat setting of 140oF in a 40 gallon hot water heater will expand by almost one-half gallon. This is because when water is heated, its density decreases and its volume expands (see below).
