JPH026490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a greenhouse heating system using an engine heat pump configured to forcefully circulate hot water between the engine heat pump and a radiator in the greenhouse.

Conventionally, in the above-mentioned device, the control means for maintaining the temperature inside the greenhouse at a set temperature combines turning the engine heat pump on and off in response to room temperature fluctuations, and controlling the engine rotation speed to maintain the hot water temperature at the outlet of the engine heat pump at the set value. However, in greenhouse heating systems in which radiator pipes are installed indoors as a radiator that uses natural convection, engine speed control is not actually performed in response to the indoor heat load.
The problem was that the engine started and stopped repeatedly due to room temperature fluctuations, leading to early wear and tear of the engine starter and early deterioration of the battery.

The reason why the above operation occurs can be explained by comparing the heat radiation characteristics A of the radiator (heat radiation tube), the heat loss characteristics B of the greenhouse, and the capacity characteristics C at each rotation speed of the engine heat pump, as shown in Figure 3. Think about it.

Now, assuming that the room temperature is constant, an equilibrium state is reached in which the heat radiation amount (QRA) of the radiator, the heat loss (QR) of the room temperature, and the heating capacity (QHP) of the engine heat pump are equal to each other (QRA = QR = QHP),
The operating conditions of the engine heat pump are characteristics A and C.
given as the intersection of Further, when the outlet hot water temperature is the set temperature Tw and the outside temperature Tab, the engine heat pump is in an equilibrium operating state at point a.

From this state, the outside temperature changes from Tab.
If the temperature rises to Tab', the heat loss in the greenhouse will decrease from Q to Q', and if the operating state of the engine heat pump follows the load, it will have to shift to point (b). However, due to the characteristics of the radiator, it actually moves to point (C) and the outlet hot water temperature decreases to Tw', so it returns to point (a) along characteristic A. and,
In actual operation, the operating condition changes even as the outside temperature rises.
The engine heat pump is maintained at point (a), and when the room temperature rises corresponding to the excess capacity (Q-Q') and reaches the upper limit of the room temperature setting range, the engine heat pump stops. Then, when the room temperature falls below the lower limit of the set range, the heat pump is activated again.

In other words, even if the outside temperature changes, the engine heat pump operates at full power at point (a) and the rotational speed does not change.

It is an object of the present invention to eliminate the drawbacks of the conventional operation described above, and to enable continuous and stable operation to be performed efficiently by controlling the engine speed according to the heating load.

The present invention is characterized in that the hot water circulation pump is operated with a constant pumping amount, and
a bypass flow path for linking an engine speed governor and an outlet hot water temperature detection sensor to maintain the outlet hot water temperature of the engine heat pump at a set value, and for limiting the flow rate from the engine heat pump to the radiator; and a valve mechanism for regulating the flow rate to the bypass flow path, the valve mechanism configured to reversibly reduce the bypass flow rate as the outside air temperature decreases based on the detection result of the sensor that detects the outside air temperature. It is equipped with a bypass flow rate control means for controlling the mechanism, and its effects are as follows.

In other words, when the outside temperature increases (or decreases) from a certain equilibrium operating state, the amount of hot water supplied to the radiator is decreased (or increased) by increasing (or decreasing) the bypass flow rate, and as a result, the amount of hot water supplied to the radiator is decreased (or increased). As the return hot water temperature to the heat pump increases (or decreases), the engine speed is controlled to decrease (or increase) in order to maintain the outlet hot water temperature constant, and the engine heat pump is operated frequently even in response to load fluctuations at low loads. This made it possible to stably perform continuous operation according to the load without causing sudden stops and starts.

Embodiments of the present invention will be described below based on the drawings.

Figure 1 shows a schematic configuration of the entire greenhouse heating system. In the figure, numeral 1 is the greenhouse, 2 is a heat radiation pipe as a natural heater laid between crop cultivation furrows, 3 is an engine heat pump, and 4 is a hot water forced circulation system. This is a pump for.

The engine heat pump 3 includes a refrigerant compressor 6, a condenser 7, an expansion valve 8, which is driven by an engine 5.
An evaporator 11 whose heat source is well water 10 supplied by a pump 9, a first heat exchanger 12 whose heat source is hot water heated by engine cooling, and a second heat exchanger whose heat source is engine exhaust gas. 13, the water introduced by the pump 4 is transferred to a condenser 7, a first heat exchanger 12, and a second heat exchanger 1.
After heating by flowing in the order of 3, the radiator 2
The supply is now circulating.

Further, a temperature sensor Si is provided near the hot water outlet of the engine heat pump 3, and the hot water outlet temperature t ₂
The speed regulating mechanism 14 of the engine 5 is controlled via a control circuit 15 so that the speed is maintained at a constant value.

Further, a bypass flow path 18 is provided between the hot water supply flow path 16 led out from the engine heat pump 3 and the return flow path 17 introduced into the heat pump 3.
At the connection point with 8, a bypass flow path 1 is connected to a part of the constant amount of hot water sent out from the heat pump 3.
8, and an electromagnetic valve mechanism 19 whose opening degree can be freely adjusted is provided to control the flow rate.

The valve mechanism 19 controls the control circuit 15 so as to control the bypass flow rate based on the detection result of the outside air temperature detection sensor _S2 provided near the greenhouse 1.
connected to the outside air temperature increases (or decreases)
The bypass flow rate is controlled to reversibly increase (or decrease) as the flow rate increases (or decreases).

Now, the heat radiation amount of the radiator 2 when it is in an equilibrium operating state at a constant room temperature is (QRA), the engine heat pump capacity is (QHP), the amount of hot water sent from the engine heat pump 3 is G ₀ , the bypass flow rate is G, and the heat pump The inlet hot water temperature is _t1 , the heat pump outlet hot water temperature is _t2 , and the outlet hot water temperature of greenhouse 1 _{is t3.}
Then, Q _RA = (G ₀ - G) (t ₂ - t ₃ ) ...(i) Q _HP = G ₀ (t ₂ - t ₁ ) ... (ii) t ₃ (G ₀ - G) + t ₂ G=t ₁ G ₀ ……(iii) t ₃ =t ₁ G ₀ −t ₂ G/G ₀ −G ……(iii)′ formula holds true. Substituting equation (iii)' into equation (i), Q _RA (G ₀ - G) (t ₂ - _{t 1} G ₀ - t ₂ G/G ₀ - G) = t ₂ (G ₀ -
G) - (t ₁ G ₀ - t ₂ G) = G ₀ (t ₂ - t ₁ ) = Q _HP . In other words, the entire engine heat pump capacity can be supplied to the greenhouse 1 regardless of the bypass flow rate.

Here, if the bypass flow rate G is increased (or decreased) when the outside air temperature increases (or decreases) and the heat load of the greenhouse 1 decreases (or increases), the inlet hot water temperature t ₁ will increase (or decrease). The temperature t ₂ also increases (or decreases), and the engine speed is controlled to decrease (or increase) in order to maintain the outlet hot water temperature t ₂ at the set temperature Tw, and the engine heat pump capacity decreases to a value according to the greenhouse load. (or increase).

For example, in Figure 3, the outside temperature is from Tab.
When increasing to Tab′, the engine speed changes from n to
n′, and an equilibrium operating state is reached at point (C).

In addition, FIG. 2 shows another embodiment. In this case, a bypass flow path 18 is provided in parallel with the circulation pump 4, and the bypass flow rate is increased in this bypass flow path 18 as the outside air temperature increases (or decreases). An electromagnetic valve mechanism 19 is provided to increase (or decrease) the heat pump capacity, and with this, it is also possible to control the increase in heat pump capacity by controlling the engine rotational speed in the same manner as described above.

[Brief explanation of drawings]

The drawings show an embodiment of a greenhouse heating device using an engine heat pump according to the present invention, and FIG. 1 is a schematic configuration diagram showing the entire greenhouse heating equipment, FIG. 2 is an overall schematic configuration diagram of another embodiment, and FIG. 3 is the heat dissipation characteristic of the radiator,
FIG. 2 is a diagram showing greenhouse heat loss characteristics and heat pump heating capacity characteristics. 1...Greenhouse, 2...Radiator, 3...Engine heat pump, 4...Hot water circulation pump, 14...
Speed governor, 18... Bypass channel, 19... Valve mechanism, 16... Hot water supply channel, 17... Return channel.

Claims (1)

[Scope of Claims] 1. A greenhouse heating device using an engine heat pump configured to forcefully circulate hot water using a pump 4 between an engine heat pump 3 and a natural heat radiator 2 in a greenhouse 1, wherein the hot water The circulation pump 4 is operated with a constant pumping amount, and the speed governor 14 of the engine 5 and the outlet hot water temperature detection sensor _S1 are linked to maintain the outlet hot water temperature of the engine heat pump 3 at the set value, Further, a bypass flow path 18 for restricting the flow rate from the engine heat pump 3 to the radiator 2 is provided, a valve mechanism 19 is provided for regulating the flow rate to the bypass flow path 18, and a sensor for detecting outside air temperature is provided.
A greenhouse heating apparatus using an engine heat pump, which is equipped with a bypass flow rate control means that controls the valve mechanism 19 to reversibly reduce the bypass flow rate as the outside air temperature decreases based on the detection result of _S2 . 2. The bypass flow path 18 is formed across a hot water supply flow path 16 led out from the engine heat pump 3 and a return flow path 17 introduced into the engine heat pump 3. Greenhouse heating equipment. 3. The greenhouse heating device according to claim 1, wherein the bypass passage 18 is provided in parallel with the circulation pump 4.