Expansion vessel · Estonian PhO 2016 #7

Physics · ideal gases

Problem

An expansion vessel is added to a heating system to avoid the overpressure forming in the system due to the expansion of water. The vessel consists of a cylinder of volume V,V, that is divided into two parts by a freely moving thin partition. One of these parts is filled with compressed air (T0=\SI20\degreeCelsiusT_{0}=\SI{20}{\degreeCelsius}) to a pressure p0p_{0}, taking under it all of the cylinder’s volume. Next, the other part of the cylinder is connected to the heating system at a temperature T1=T0T_{1}=T_{0} and the system is filled with water until a pressure p1=\SI300kPap_{1}=\SI{300}{kPa} is reached and the total volume of the water in the system is Vs=\SI100LV_{s}=\SI{100}{L}. After this β=10%\beta=10\% of the expansion vessel is filled with water. In winter the volume of the water in the system increases by α=\SI1%\alpha=\SI{1}{\%} due to the heating and in result the pressure of the system increases to p2p_{2}, moreover the air in the expansion vessel is warmed to a temperature T2=\SI40\degreeCelsiusT_{2}=\SI{40}{\degreeCelsius}. Find how big must be the initial air pressure p0p_{0} in the expansion vessel and the minimal volume of the vessel VV, so that the extra pressure Δp=p2−p1\Delta p=p_{2}-p_{1} formed in result of the water’s expansion would not be bigger than 50 kPa.

Related theory

Browse the problem library