Methods of heat engineering tests for thermal hydrodynamic pumps.

Размещено на http://www.allbest.ru/

Methods of heat engineering tests for thermal hydrodynamic pumps

Before starting any discussion it is necessary to coordinate the terms, as each of the participants of discussion can use the same term for absolutely different phenomenons. Within the subjects considered in this article two terms are most widely interpreted: Efficiency (coefficient of efficiency) and CP (coefficient of performance). It is necessary to emphasize especially that depending on range of application these concepts have various meaning, and nobody can neither cancel nor prohibit this hands-on experience.

Practically everyone remembers the term “efficiency” from the school physics textbook, where it has been told that the greatest possible efficiency is gained in the direct thermodynamic Carnot cycle, and it cannot be above 1. But the majority do not remember any more that for inverse cycle Carnot used the term CP, which value is above 1 just by definition.

Technics development caused a necessity of comparison of characteristics of different by design but equal by purpose devices. Therefore the terms “efficiency and CP” have gained more wide usage (not only for devices operating by the Carnot cycle), their meaning has considerably changed in comparison with that S.Carnot put in these definitions. For example it is used at least 6 definitions for boiler-house efficiency:

1. Burning efficiency - quantity of fuel energy which is released at burning (approximately 93-95%);

2. Boiler-house efficiency - quantity of fuel energy which is effectively used, i.e. converted to another energy carrier medium (on 10-15% lower than burning efficiency);

3. Furnace technics efficiency - shows how burning and heat reception in a boiler-house effective (furnace technics efficiency and boiler-house efficiency are approximately equal);

4. Installation efficiency - ratio between total effective energy and total energy of installation efficiency. The total energy includes also “auxiliary energy”, for example: electric energy necessary for pumps operation in a boiler-house, ventilation, flues etc. Thus it will be on 1-5% lower than boiler-house efficiency.

5. System efficiency - expands system limits to:

- heat production with loss;

- heat distribution with loss in heating mains, etc;

- heat utilization.

6. Annual efficiency - basically matches boiler-house efficiency, but the average boiler-house efficiency for the whole year is calculated. The annual efficiency also includes periods with low level of burning, for example boiler-house start, etc.

Technology development has led to paradoxical situations, when efficiency > 1. For example according to State Standard 21563-93 condenser boilers have efficiency = 108-109% [1].

Electric energy is converted to mechanical energy of rotation in thermal hydrodynamic pumps (“vortex heat-generators”), and then to thermal energy of heating of heat-transfer fluid (water). Though [2] there are cases of use of the term of efficiency with reference to “vortex heat-generators” in some publications, we consider it incorrect in essence. In spite of the fact that we face water every second, it remains little-studied and conceals a lot of enigmas. For example water can have various structure and change it under external effecting even under the influence of human speech, has “memory”, etc. Ice has about seventy aggregate states, and the quantity of water states can achieve two thousand. Till now is not clear exactly what processes occur with water in the activator of the thermal hydrodynamic pump, how it changes, there is no theoretical model of heating process confirmed in practice [3, 4]. It is possible to assert on the basis of practical experience that gas and water mix, but not water, comes from a heat-generator. And as the system is hydraulically closed, and air input does not occur, gas bubbles are the product of centrifugal force effecting on heat carrier flow. Accumulated actual data allows to put forward a hypothesis that thermal hydrodynamic pumps are “energetically open” devices, i.e. they take energy from the outside. Water passing the heat supply system reverts to the original state under effecting of forces: gravitational, molecular interaction or other not known for the present.

The following facts testify in favor of the “energetical openness” hypothesis:

- Heat release process does not end in the activator, and continues in the pipeline of a heat supply system. During experiments it has been fixed, that the heat carrier temperature raises as moves away from the activator discharge connection. If the water “relaxation” process in the system did not end completely, then there was a sharp decrease in a heating gradient starting from the moment of “non-relaxed” mixes entry in the activator.

- After power cutoff the heat carrier temperature raises during some time [5]. The time and value of heat carrier “postheating” depends on several factors: power of device, heat carrier volume in the system, temperatures of heat carrier at the moment of the device shut down, etc. It is possible to insist that this “postheating” is not connected with time lag of thermometers, but caused by continuation of the heat release process.

In this connection there are big technical and methodological complexities in definition of heating efficiency of thermal hydrodynamic pumps.

It is necessary to understand that there are two fundamentally different approaches to tests of thermal hydrodynamic pumps:

- confirmation of working capacity of a concrete product;

- calculation of nominal (certified) heating efficiency for concrete type of design.

A measurement procedure and composition of the test unit equipment will be different depending on an assigned task. The methods of working capacity confirmation are simple enough and proven, but there are no standard test methods for calculation of nominal (certified) heating efficiency of concrete type of design for now.

Working capacity of the thermal hydrodynamic pump can be checked most simply as follows: temperatures in inlet and outlet fittings of the activator are measured at the recommended volume of pumping specified in Table 1, where the installation capacity means electric motor installed capacity.

Table 1

Depending on the heat carrier temperature on the inlet fitting and the pumping volume for one pass through the activator heat carrier heats up on 14 - 24°С. Thus the lower the heat carrier temperature is in the activator inlet the less heating gradient is. If the measured gradient is in the set temperature range, the thermal hydrodynamic pump is considered serviceable.

Heat supply system large influence on the heat release process: hydroresistance in output maim, pumping speed, heat carrier volume in the system, length and branching of pipelines, etc. Therefore incorrectly designed circuit of a heat supply system and incorrectly selected modes can reduce heating efficiency of a “vortex heat-generator”, moreover completely break the heat release process.

For example, in October, 2007 it consumed 11.0kW-hour of electric power at electric motor installed capacity of 7.5kW at tests in the Lappeenranta Technological University (Finland). According its design heating efficiency was low. As a result of situation it was defined that the latch in the outlet main was practically closed for the purpose of decrease of pumping volume to increase the heating gradient. After opening the latch the power consumption decreased to 6.8kW-hour without essential decrease in the heating gradient.

Too large pumping volume (in 3-5 times above the recommended one) leads to “break” of the heat release process, the heating gradient sharply decreases.

Large volume of heat carrier in the system also reduces the system heating efficiency. While tests in Orel temperature in premises rose, when quantity of radiators - and consequently the water volume - was decreased. Practically optimum water volume in a system for TS1-055 is 0.5 - 1.0m3. Heat carrier in such volume can make 3-6 passes through the activator per hour.

Oxygen released from water in the course of operation reduces heat release and raises working pressure in a system, therefore must be constantly expelled from the system, and besides feeding the system with “fresh” water must be the minimum.

In case of problems in a heat supply system the method of heating gradient indication allows to check the installation working capacity fast and with the minimum expenses.

The manufacturer defines working capacity of each serial TS1 type thermal hydrodynamic pump by the following method:

1. Fill 400kg of water through funnel В1 to the tank using a measuring vessel and commercial scale with error + 0.1kg.

2. Set pressure 0.3MPa using the circulating pump in the pressure water pipeline.

3. Upon reaching water temperature in the centre of its volume of 30 + 2°С turn on stopwatch and measure the time interval Т necessary for heating water in the hydraulic system of the test unit to 80 + 2°С. Water mixing in the tank to prevent thermal stratification of water is provided by mounting of the inlet main fitting in the bottom part of the tank, and the delivery pipe fitting in the top part.

4. Shat down the electric motor and the circulating pump at water temperature of 80 + 2°С. Discharge hot water from the tank through a drainage tube and funnel В2 to the sewerage.

The test unit diagram is shown in Fig. 1, and its general view in Photo 1.

While conducting acceptance tests in the other commercial plant 1000kg of water is heated up from actual temperature of filling 10 - 17°С to 80 + 2°С, and the heating time is measured. The average heating time for 1000 kg of waters makes: 80-90 minutes - for TS1-055; 55-60 minutes - TS1-075, 45-55 minutes - TS1-090.

Fig. 1. Test unit diagram

Photo 1. Test unit general view

Such tests are quite enough for confirming of working capacity of a concrete product. However, design of the factory stand and the tests methods presented above do not allow to carry out heating efficiency calculation, a special certified test unit and other method are necessary for this purpose.

The tests method for calculation of nominal (certified) heating efficiency of a concrete type of design must consider the following basic points:

1. While starting the thermal hydrodynamic pump the electric motor require the raised power for initial spinup of the shaft, which has a large inertia moment, and overcoming of viscosity of non-heated heat carrier in the activator. After the thermal installation transfers to the operating mode, the power consumption drops on 6-10%. Therefore measurement of parameters must be conducted at the set operating mode.

2. If the temperature of heat carrier delivered to the activator is not essential for confirmation of working capacity, the water temperature must be in the range 60 + 10°C in the tests intended for calculation of nominal (certified) heating efficiency. It is caused by the following reasons:

- it is a real range of operational temperatures for intrabuilding heating systems;

- as practice shows, water heating in different temperature range require different quantity of energy. Water heating to +20°C requires the highest power inputs, power inputs for heating are the minimum at water temperature of +63°C.

Therefore all tests conducted in the range of relatively low reheat temperature of water, will obviously give underrated results of heating efficiency.

3. The account of produced energy must not be made before the power cutoff, but before the moment when heat carrier achieves the maximum temperature.

4. While heating efficiency calculation it is necessary to consider stand heat loss in the course of conducting the tests. Professor, D.E., Nikitskiy V.P. has offered an original method for account of this heat loss, which will be published in the near future.

5. Presence in the system of water-gas-vacuum mix with much smaller density than water is a reason that water consumption indicators can not measure real heat carrier consumption. Therefore:

- consumption indicators must be installed directly ahead of the activator inlet fitting, and a “damper” providing full “relaxation” of heat carrier must be mounted ahead of consumption indicators;

- some consumption indicators with different methods of measurement must be installed approximately with each other, and it is necessary to compare their indications;

- use indications of consumption indicators as help information only.

Depending on the assigned task, having the same actual data obtained during an experiment with not difficult manipulations it is possible to make opposite conclusions. Therefore opponents of “vortex heat-generators” deliberately conduct tests under conditions considerably worst than the optimum, do not take into account additional factors such as “postheating” and stand heat loss, and if get good result anyway, do not recognize it [9,10].

Photo 2. General view of typical heat supply station

Photo 3. General view of BBHSS-55.

Practitioners have little interest in academic disputes concerning values of efficiency and CP. They are more interested in the economy, which will be brought by transfer to the heat supply by means of thermal hydrodynamic pumps. Comparison of heat supply costs, which we conducted on the basis of six-years operating experience, show that with thermal hydrodynamic pumps they are lower in 3-5 times than with heating coil and electrode boilers, in 8-10 times than diesel, and in 3-5 times than centralized heating .

For the integrated selection of power of the thermal installations applied to heating Construction regulations specify - 1kW delivered thermal energy per 10sq.m of heated area. For selection of power of TS1 thermal hydrodynamic pump this specification is 1kW of the pump electric motor installed capacity per 30sq.m of heated area. Consumed electric power of the electric motor decreases on 10-15% in typical operation. Proceeding from the integrated specification thermal installations must heat conditional typical (matching the requirements of Construction regulations) residential, household, cultural-entertaining premises, premises of industrial-economic purposes, etc., of volume: TS1-055 - 5180m3, TS1-075 - 7060m3, TS1-090 - 8450m3, TS1-110 - 10200m3 (marking indicates the electric motor power).

Necessary temperature mode can be maintained in heated premises. For example, 20 - 22°C for living spaces, 15 - 18°C - industrial spaces, 8 - 12°C - warehouse. Temperature mode regulating is made by setting the heat carrier temperature range. As heat carrier heats up to the set maximum temperature the thermal hydrodynamic pump turns off, as heat carrier cools to the minimum set temperature - turns on. Heating system generates exactly as much thermal energy as much heat loss of a heated object. During winter periods the operating time is more and less for autumn-spring periods. For the average heating season heating system operates 25-30% of time. Therefore we apply factor Koper. = 0.3 to integrated calculation of financial expenditure for heating.

Automatics allow to make change-over of a temperature mode within a minute. In the evening a duty engineer can lower temperature in premises and before the beginning of working day set comfortable temperature in premises again. It allows additionally lower heating cost.

For the integrated selection calculation is conducted by the minimum possible temperature. As the average climatic temperature for a heating season is higher, real 1kW heats up considerably larger volume. Some actual data is presented in Table 2.

Table 2

Note: the table is made according to the users' references presented on the website: http://www.ratron.su, section “Products” / “References”.

From the economic point of view TS type thermal hydrodynamic pumps are appropriate for using at a construction stage also. Mobile building block heat supply stations (BBHSS) are developed to provide the site with heat from the very beginning of construction.

The general view of the pilot BBHSS-55 intended in this concrete case for air heating of derricks is shown in Photo 2. A heat thermal hydrodynamic pump TS1-055 with the installed electric motor power of 55kW, heating heat-transfer fluid and heat removing air-heating assembly on the basis of hot-air heater KSk are mounted in BBHSS-55. Heat carrier volume in the system is 70 liters. Outdoor air passing the hot-air heater heats up to temperature of +70°C and is discharged under pressure to the heated premises.

Originally according to the customer's requirements air-heating assembly AO2-10 with heat capacity of 116kW, i.e. with cooling in 2.1 times more than the TS1-055 installed electric power was mounted in BBHSS-55. At tests heat-transfer fluid heated up to the maximum temperature + 95°C for 5 minutes then there was automatic shutdown of TS1-055. For the next 5 minutes AO2-10 removed the produced heat downgrading temperature of the heat-transfer fluid to +70°C, TS1-055 switched on. The process repeated in 5 minutes. Such frequency of turning on/off is not allowed for a powerful electric motor, therefore the solution to change AO2-10 for a more powerful AO2-20 assembly with heat capacity of 220.4kW that four times more than the electric motor installed capacity of the thermal hydrodynamic pump was accepted. In the course of acceptance tests at ambient temperature - 2°C installation worked for 17 minutes from a cold condition till shut down. At repeated starts-up heating up to the maximum temperature occurred for 13 minutes that testifies about incomplete heat removal. Now our company is conducting full-scale tests of the pilot mobile BBHSS-55 for heating derricks. Perfection of BBHSS proceeds, however already gained experience shows its high efficiency.

Practice is a criterion of true. And practice shows that thermal hydrodynamic pumps have good prospects of development. Therefore the problems, which have been not solved today, will be surely solved tomorrow.

The literature

test thermal hydrodynamic pump

1. С.В. Козлов. «Может ли КПД быть больше единицы?»

- «Энерго Info», № 4, апрель 2007 г, стр. 86-88.;

- «Энергетика Сибири», № 2 (13) апрель, 2007 г., стр.11-15.

2. С. Кашницкий «Нас согреет вакуум». «Аргументы и Факты», № 8 (1321), 2006 г., стр. 49.

3. С.В. Козлов. «Наукой не доказано». «Коммунальный комплекс России», № 7 (25), июль 2006 г., стр. 70-73.

4. С.В. Козлов. «Для тех, кто хочет знать, что такое «вихревой теплогенератор». «Энергетика Сибири», № 3(8), июнь 2006 г., стр. 32-34.

5. С.В. Козлов. Проблемы выбора современной системы теплоснабжения. «Энергетика Татарстана», № 2(6) 2007 г., стр. 38-46.

6. С.В. Козлов. О необходимости сертификации. «Стандарты и качество», № 5, май 2007 г., стр. 55.

7. С.В. Козлов. Инновационные технологии отопления - тепловые гидродинамические насосы. «ТехноМир», № 3 (33), 207 г., стр. 24-26.

8. С.В. Козлов. Основные принципы выбора системы теплоснабжения. «Коммунальщик», № 3 март, 2007 г., стр. 54-60.

Размещено на Allbest.ru