A method for reacting silicon tetrachloride and hydrogen comprised in a reactor feed gas and exchanging heat between the reactor feed gas and a reactor product gas comprising trichlorosilane and hydrogen chloride, the reaction and heat exchange occurring in a reactor apparatus, the reactor apparatus comprising: a reaction vessel having a wall and comprising a reaction chamber in which the reaction occurs; and a shell and tube heat exchanger for transferring heat between the reactor feed gas and product gas, the shell and tube heat exchanger comprising: a shell that is in fluid communication with the reaction chamber; a tube bundle within the shell, the tube bundle extending through the wall into the reaction vessel, the bundle comprising a plurality of central tubes and a plurality of peripheral tubes between the central tubes and the shell, the tubes being in fluid communication with the reaction chamber; a chamber formed between the tube bundle and the shell; and a reactor feed gas discharge and a reactor product gas inlet, the reactor feed gas discharge being above the reactor product gas inlet, the method comprising: introducing the reactor feed gas into the peripheral tubes and central tubes of the shell and tube heat exchanger, the reactor feed gas comprising silicon tetrachloride and hydrogen; discharging the reactor feed gas comprising silicon tetrachloride and hydrogen into the reaction vessel to cause silicon tetrachloride and hydrogen to react and to form the reactor product gas, the reactor product gas comprising trichlorosilane and hydrogen chloride; introducing the reactor product gas into the chamber formed between the tube bundle and the shell; and discharging the reactor product gas from the shell. a reaction vessel having a wall and comprising a reaction chamber in which the reaction occurs; and a shell and tube heat exchanger for transferring heat between the reactor feed gas and product gas, the shell and tube heat exchanger comprising: a shell that is in fluid communication with the reaction chamber; a tube bundle within the shell, the tube bundle extending through the wall into the reaction vessel, the bundle comprising a plurality of central tubes and a plurality of peripheral tubes between the central tubes and the shell, the tubes being in fluid communication with the reaction chamber; a chamber formed between the tube bundle and the shell; and a reactor feed gas discharge and a reactor product gas inlet, the reactor feed gas discharge being above the reactor product gas inlet, a shell that is in fluid communication with the reaction chamber; a tube bundle within the shell, the tube bundle extending through the wall into the reaction vessel, the bundle comprising a plurality of central tubes and a plurality of peripheral tubes between the central tubes and the shell, the tubes being in fluid communication with the reaction chamber; a chamber formed between the tube bundle and the shell; and a reactor feed gas discharge and a reactor product gas inlet, the reactor feed gas discharge being above the reactor product gas inlet, introducing the reactor feed gas into the peripheral tubes and central tubes of the shell and tube heat exchanger, the reactor feed gas comprising silicon tetrachloride and hydrogen; discharging the reactor feed gas comprising silicon tetrachloride and hydrogen into the reaction vessel to cause silicon tetrachloride and hydrogen to react and to form the reactor product gas, the reactor product gas comprising trichlorosilane and hydrogen chloride; introducing the reactor product gas into the chamber formed between the tube bundle and the shell; and discharging the reactor product gas from the shell.