US 4,374,506 A · Automatic flue gas heat recovery system

Abstract

An automatic flue gas heat recovery system for supplementing or replacing a conventional, separate hot water system. In the example described, the heat recovery system is applied to a pizza restaurant where large quantities of heat energy are normally wasted up an oven chimney stack, and large quantities of hot water also are required for restaurant operations. An electric motor driven pump circulates water in a closed loop between a storage tank and a heat exchanger tube located in the oven chimney stack. A thermostat control automatically starts the pump when the oven heats the chimney stack to an effective water heating temperature. When temperature in the storage tank reaches a predetermined maximum, the thermostat control stops the pump, opens a drain valve, and dumps water quickly and completely from the heat exchanger tube. Three different embodiments are shown and described illustrating systems with one or more storage tanks and one or more pumps. In the plural storage tank embodiments, an existing hot water heating tank may be converted for use to augment a main tank supplied with the present system.

Claims13

Dependent claims

In an automatic flue gas heat recovery system:

a heat exchanger housing adapted to be positioned in a flue gas flow from a heat source;
heat exchanger tube means in said housing;
hot water storage tank means;
water inlet and outlet conduits connected to the hot water storage tank means;
conduit means including at least two conduits connecting the tank means with the heat exchanger tube means to provide a closed loop for circulating water therebetween;
motor driven pump means in said conduit means effective when activated to circulate water in the closed loop;
drain valve means being activatable between opened and closed conditions and connected to said conduit means in position to drain said heat exchanger tube means when opened;
and
means for de-activating said pump means and opening said drain valve means in response to a temperature in said storage tank means exceeding a predetermined value.

6 more elements

In an automatic flue gas heat recovery system:

a heat exchanger housing adapted to be positioned in a flue gas flow from a heat source;
heat exchanger tube means in said housing;
hot water storage tank means;
water inlet and outlet conduits connected to the hot water storage tank means;
conduit means including at least two conduits connecting the tank means with the heat exchanger tube means to provide a closed loop for circulating water therebetween;
motor driven pump means in said conduit means effective when activated to circulate water in the closed loop;
drain valve means being activatable between opened and closed conditions and connected to said conduit means in position to drain said heat exchanger tube means when opened;
thermostat control means including temperature sensor means associated with the storage tank means and connected to the pump means and drain valve means to control activation thereof;
control means including means for activating said pump means and closing said drain valve means in response to the operational status of the heat source;
and
said thermostat control means including means for deactivating said pump means and opening said drain valve means in response to a temperature in said storage tank means exceeding a predetermined value.

8 more elements

In an automatic flue gas heat recovery system:

a heat exchanger housing adapted to be positioned in a flue gas flow from a heat source;
heat exchanger tube means in said housing;
hot water storage tank means including main tank means and auxiliary tank means, at least said auxiliary tank means having heating means therein;
water inlet and outlet conduits connected to the hot water storage tank means;
conduit means including main conduit means connecting the main tank means with the heat exchanger tube means to provide a main closed loop for circulating water therebetween, and auxiliary conduit means connecting the two tank means to provide an auxiliary closed loop for circulating water therebetween;
motor driven pump means including main and auxiliary pump means in said main and auxiliary conduit means respectively, said pump means being effective when activated to circulate water in the respective closed loops;
drain valve means being activatable between opened and closed conditions and connected to said main conduit means in position to drain said heat exchanger tube means when opened;
thermostat control means including temperature sensors associated with the heat exchanger housing and hot water storage tank means and connected to the pump means and drain valve means to control activation thereof;
said thermostat control means including means for activating said main pump means and closing said drain valve means in response to a predetermined temperature in said heat exchanger housing;
said thermostat control means including means for activating said auxiliary pump means in response to a predetermined temperature in said main tank means;
and
said thermostat control means including means for deactivating both of said pump means and opening said drain valve means in response to a predetermined temperature in one of said tank means.

9 more elements

Dependencies are inferred from the claim text.

Automatic flue gas heat recovery system

Life of this patent

Automatic flue gas heat recovery system

Life of this patent

Abstract

Claims13