RU2812554C1 - Autonomous hot water preparation system for several water delivery points - Google Patents

Abstract

FIELD: thermal energy.

SUBSTANCE: invention can be used in boilers for heating and hot water preparation, in instantaneous gas and electric water heaters, in autonomous heating and hot water supply systems. A buffer tank made of heat-conducting material is attached to the output pipe of a thermal generator for hot water production, with an output pipe for connecting to the consumer’s internal water supply networks with a capacity of 1.5-3.5 litres, through which water heated by the thermal generator flows, the buffer tank is equipped with a plate thermistor heating element pressed to its outer surface with a power of 20-100 Watts with a positive thermal coefficient.

EFFECT: smoothing out temperature fluctuations at water intake points of an autonomous heat supply system.

2 cl, 1 dwg

Description

Field of technology to which the invention relates

The present invention relates to the field of thermal energy, in particular to gas wall boilers for heating and preparing hot water, instantaneous gas water heaters, instantaneous electric water heaters, and can be used in autonomous heating and hot water supply systems for individual houses, apartments in buildings with different heights and number of floors.

State of the art

The standard rated power of wall-mounted boilers in hot water preparation mode and instantaneous gas water heaters is 24 kilowatts per hour, which allows the use of these devices to produce hot water with a flow rate of about 11 liters per minute with heating the water temperature by 25 degrees Celsius. From the point of view of hot water consumption, this is enough for one point of analysis. A modern household is equipped with at least two hot water points, located in the bathroom and kitchen. In the bathroom, as a rule, a shower or bathtub and sink are installed separately, but the simultaneous use of a shower and sink in the bathroom is extremely rare. All water distribution points are equipped with valve or single-lever faucets. Water consumption when using a shower is 6-13 liters per minute with an average duration of single use of 5-7 minutes. Using a kitchen sink mixer tap occurs at an average flow rate of 4 liters per minute with an average duration of 2 minutes to 6 minutes. From the above it follows that the simultaneous use of two water collection points in an autonomous heating system equipped with standard wall-mounted gas boilers or gas instantaneous water heaters, electric instantaneous water heaters with a rated thermal power of 24 kilowatts per hour is possible only in economy mode with limited costs. Comfortable consumption of hot water in an individual heating system with the possibility of simultaneous use of two points of analysis is only possible if there is a thermal energy generator with a rated power of 28-32 kilowatts per hour. In these cases, it is possible to provide hot water flow up to 18-20 liters per minute.

The issue of using both instantaneous water heaters and wall-mounted boilers in DHW mode for several points of hot water collection is also related to the thermal inertia of these devices. Heat exchangers of gas heat generators have a mass of 1.5-3 kilograms, are made of copper or stainless steel, the wall thickness of the heat exchanger pipes is 0.8-1 mm (Toropov A.L., “Autonomous low-power heat supply systems. Wall-mounted gas boilers and heat accumulators ". - Publishing house MISI - MGSU, 2022. - 176 pp. ISBN 978-5-7264-3110-9 and Toropov A.L., "Wall-mounted gas boilers of autonomous heat supply systems. History of creation. Basic elements. Classification. Part 1. Convection wall-mounted gas boilers. - - M.: Publishing House of the Academy of Natural Sciences, 2020. - 60 pp. ISBN 978-5-91327-630-8 DOI 10.17513/pr.411). The ability to modulate the thermal power of a heat generator burner does not solve the issue of significant temperature fluctuations at points of consumption when using water mixers. Abruptly closing or opening the tap of the second point of consumption while simultaneously using the first leads to temperature jumps of up to 10 degrees Celsius, which can even lead to minor skin burns or a sharp cooling of the consumed water. Electronic modulation of thermal power is not able to eliminate the influence of thermal inertia of the primary heat exchanger of a wall-mounted boiler or instantaneous water heater. The most critical thing when using gas instantaneous water heaters with several hot water distribution points, from a comfort standpoint, is the use of a shower and sink faucet in the kitchen. If the shower head consumes 10 liters of water per minute and the kitchen tap consumes 4 liters per minute, a sharp change in the flow of hot water associated with closing the tap in the kitchen sink will lead to a change in temperature in the shower tap of about 7 degrees Celsius. When the initial water temperature in the shower is 40 degrees Celsius, an instant and unexpected change in water temperature to 47 degrees Celsius is perceived as “boiling water”. Instantaneous gas water heaters that are not equipped with thermal power modulation devices cannot be used in hot water supply systems for households with several hot water collection points, since adjusting the temperature when changing water consumption requires manually changing the gas flow directly at the water heater. Instantaneous water heaters with thermal power modulation process changes in thermal load in 2-6 seconds, the influence of thermal inertia of heat exchangers increases this time to 4-11 seconds. The magnitude of the temperature change in the shower during periodic simultaneous use of a remote sink in the kitchen depends on the rate of change in the hot water flow rate in the sink, the thermal inertia of the heat exchangers of the heat generators, thermal power modulation algorithms, the thermal inertia and sensitivity of temperature sensors, the factory settings of the gas valve and its hysteresis.

A wall-mounted gas heating boiler is known (see patent RU No. 2452906, IPC F24H 1/08, published 06/10/2012). A boiler for heating and/or hot water supply, containing an expansion tank and a sealed housing in which a combustion chamber with a gas burner is located, a heating circuit heat exchanger with a smoke box, a buffer tank with a hot water supply circuit heat exchanger, pipes for supplying air to the firebox to the gas burner and removal of combustion products located in the upper part of the boiler, coolant inlet and outlet pipes and water inlet and outlet pipes, and a control system, characterized in that the heating circuit heat exchanger includes a prismatic body with an open lower part, a tube sheet in the upper part and a coil on the outer surface , the smoke box at the point of its connection with the pipe for removing combustion products is equipped with a channel connected to the internal cavity of the sealed housing, and the buffer tank is connected to the coolant outlet pipe and includes a prismatic body with a heat exchanger of the hot water supply circuit located inside it and its own pipes for supplying and removing coolant and water inlet and outlet, while the buffer tank is moved outside the location of the heating circuit heat exchanger, placed in the lower part of the sealed housing and, through an additional pipe, through a valve switching to the “heating + hot water supply / hot water supply only” mode, is connected to the coolant supply pipe, on which after connecting it to the additional pipe of the buffer tank, a pump is installed.

The disadvantage of this boiler is the lack of a device for maintaining temperature during pauses between hot water consumption. When consuming hot water after a long pause lasting more than 1-2 hours, the water in the buffer tank cools down and it takes time to warm it up. When re-used after a short pause, for example, closing the hot water consumption tap and reopening after a few seconds, there is a technological pause in the operating algorithms of gas boilers associated with blocking repeated short-term starts of the boiler gas burner for 30 seconds (Toropov A.L., “ Autonomous low-power heat supply systems. Wall-mounted gas boilers and heat accumulators." - MISI Publishing House - MGSU, 2022. - 176 pp. ISBN 978-5-7264-3110-9). The capacity of the buffer tank of the proposed design is not enough to maintain a stable hot water temperature, which leads to significant discomfort when consuming hot water.

The design of the water heater that is closest in technical essence to the proposed model (see patent RU No. 2496061, IPC F24H 1/20, publ. 10.20.2013). A water heating system with a gas water heating device that is connected to a cold water inlet pipe and a hot water outlet pipe, containing an electric storage type water heater built in series in the hot water outlet pipe and equipped with a thermostat. An electric water heater is installed inside a gas water heating device and has a volume of less than 20 liters. The housing of the storage tank of the electric water heater is covered with heat-insulating material. The disadvantage of this design is low maintainability and high economic costs in the event of failure of the electrical heating elements. Another disadvantage is the large recommended volume (upper limit) of an electric water heater, the largest value of which is 20 liters. This volume significantly increases the size of the heat generator, its overall weight and cost.

Disclosure of the invention

The technical task of the proposed invention is to solve the problem of smoothing temperature fluctuations at water collection points of an autonomous household water supply system while simultaneously using different water collection points at random in time with adjusting water flow and its temperature using mixers of arbitrary design.

The solution to the issue of preparing hot water with wall-mounted heat generators is possible by using a buffer tank installed in the body of the heat generator, from which hot water is collected. Hot water, prepared in a burner device or an electric heat exchanger, enters a buffer tank, mixes with water in the tank and is supplied to the consumer through the boiler outlet. The recommended volume of the buffer tank for systems with two points of analysis is 1.5-3.5 liters, since a large volume of the buffer tank will increase the dimensions of the boiler, and a smaller volume will not be sufficient to smooth out sudden changes in hot water consumption at several points of analysis. The minimum value of the buffer tank volume is determined by the time of the heat generator power modulation algorithm when changing from minimum values to maximum values, plus 1.5 liters. For example, the time for the growth of the thermal power of a gas boiler when preparing hot water at the start of heating until reaching maximum power is 6 seconds. With a maximum consumption of two water points of 20 liters per minute, the volume of water in 6 seconds will be 2 liters. The volume of the buffer tank should be 2 liters plus 1.5 liters, for a total of 3 liters. If the thermal power is turned on instantly, as when using a single electric heating element, then the volume of the buffer tank is 1.5 liters.

The problem of using a buffer tank for preparing hot water in wall-mounted boilers is due to the fact that during long pauses in the consumption of hot water, in such cases as the absence of users, the night period, the water in the buffer tank cools down and it will take up to 10 minutes to warm it up when the water heater is turned on. seconds Thermal insulation of the buffer tank does not completely solve the issue, since pauses in the consumption of hot water can take a long time during which the water cools down. The technical problem of the proposed invention is also to solve the issue of maintaining the temperature in the buffer tank during pauses between the consumption of hot water. The use of electrical tubular resistor elements to maintain the temperature in the buffer tank at 40 degrees Celsius is ineffective. In flow-through heaters, water contains hardness salts, which are deposited in the form of scale on the most heated surfaces. Tubular heating elements, in the absence of water movement in the buffer tank during pauses between water consumption, cause the layer of water in contact with them to boil when heated, which contributes to the growth of scale on the surface of the tubular element, leading to loss of heating efficiency and its rapid failure. The use of surface-type resistor heating elements (“heating wire”) requires the installation of thermostats, which complicates the design of the water heater.

The technical result of the proposed invention is achieved by attaching to the surface of a buffer tank made of a material with high thermal conductivity, thermistor RTS heating elements that have self-regulation of heating intensity. When the temperature in the buffer tank rises above the set temperature of 40 degrees Celsius, the ohmic resistance of the thermistor with a positive thermal coefficient (PTC) increases sharply and the buffer tank is not heated by the thermistor PTC element.

Brief description of the drawings.

Figure 1 shows a diagram of the proposed invention.

1. Thermal generator for hot water production.

2. Inlet pipe

3. Outlet pipe

4. Thermal power modulation system.

5. Buffer capacity.

6. Connection pipe to internal water supply networks.

7. Thermistor heating element with positive thermal coefficient.

8. Thermal insulation material.

Carrying out the invention

Cold water of the water supply system (not shown in figure 1) enters the heat generator for the production of hot water 1 through the inlet pipe 2, is heated by the heat generator for the production of hot water 1 and exits through the outlet pipe 3, to which a buffer tank 5 with a volume of 1.5-3 is attached .5 liters. The heated water flows through the connection pipe to the internal water supply networks 6 of the consumer. The consumer uses hot water for his needs by mixing hot and cold water through mixers of any design with the possibility of using several water intake points simultaneously. When using several water taps randomly over time, a sharp change in hot water flow occurs. Due to the thermal inertia of the hot water production thermal generator 1, the thermal power modulation system 4 needs time to change the thermal energy generation power in accordance with the changed water flow flowing through the hot water production thermal generator 1.

The technical result of the task of smoothing temperature fluctuations at water intake points of an autonomous household heat supply system with simultaneous random use of different water intake points with adjustment of water flow and its temperature using mixers of arbitrary design is achieved by installing a buffer tank 5 with a volume of 1.5-3.5 liters, performed made of thermally conductive material with a plate thermistor heating element with a positive thermal coefficient 7 with a power of 20-100 Watts placed on its outer surface to maintain the temperature of hot water in the buffer tank 5 during periods of no hot water consumption. To reduce heat losses and increase energy efficiency, the buffer tank 5 is covered with a layer of heat-insulating material 8.

The proposed invention compared to the prototype and other known technical solutions has the following advantages:

- the presence of a device for maintaining temperature during pauses between hot water consumption;

- smoothing temperature fluctuations at water collection points of an autonomous water supply system with simultaneous random use of different water collection points;

- high maintainability;

- low economic costs in case of failure of electric heating elements;

- small recommended volume of buffer tank, which does not increase the size of the heat generator, its total weight and cost.

Since the claimed invention differs from the closest analogue in a number of significant features, it meets the patentability condition of “novelty”. The claimed invention is based on the known laws of the material world, which allows us to assert that the invention complies with the condition of “industrial applicability”.

Since the prior art does not know an autonomous system for preparing hot water for several points of analysis with a buffer tank with a plate thermistor heating element placed on its outer surface to maintain the temperature of hot water, we can conclude that the claimed device and method comply with the patentability condition “inventive step”.

Claims (2)

1. Autonomous hot water preparation system for several water collection points, consisting of a thermal generator for hot water production, inlet and outlet pipes, a thermal power modulation system depending on the required amount of thermal energy for heating water, characterized in that to the output pipe of the heat generator hot water is connected to a buffer tank made of heat-conducting material, with an outlet pipe for connecting to the internal water supply networks of the consumer, with a capacity of 1.5-3.5 liters, through which water heated by a heat generator flows, the buffer tank is equipped with a plate thermistor pressed to its outer surface , with a positive thermal coefficient, a heating element with a power of 20-100 watts. 2. Autonomous hot water preparation system according to claim 1, characterized in that the buffer tank is covered over the entire outer surface with heat-insulating material.

Images